[ Upstream commit 29ccaa4b35 ]
Commit d768bd892f ("s390: add options to change branch prediction
behaviour for the kernel") introduced .Lsie_exit label - supposedly
to fence off SIE instruction. However, the corresponding address
range length .Lsie_crit_mcck_length was not updated, which led to
BPON code potentionally marked with CIF_MCCK_GUEST flag.
Both .Lsie_exit and .Lsie_crit_mcck_length were removed with commit
0b0ed657fe ("s390: remove critical section cleanup from entry.S"),
but the issue persisted - currently BPOFF and BPENTER macros might
get wrongly considered by the machine check handler as a guest.
Fixes: d768bd892f ("s390: add options to change branch prediction behaviour for the kernel")
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Make the oklabel within the CHKSTG macro local. This makes sure that
tools like objdump and the crash debugging tool still disassemble full
functions where the macro has been used instead of stopping half way
where such a global label is used and one has to guess how to
disassemble the rest of such a function:
E.g.:
0000000000cb0270 <mcck_int_handler>:
cb0270: b2 05 03 20 stck 800
...
cb0354: a7 74 00 97 jne cb0482 <oklabel270+0xe2>
0000000000cb0358 <oklabel243>:
cb0358: c0 e0 00 22 4e 8f larl %r14,10fa076 <opcode+0x2558>
...
Fixes: d35925b349 ("s390/mcck: move storage error checks to assembler")
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
The restart interrupt is triggered whenever a secondary CPU is
brought online, a remote function call dispatched from another
CPU or a manual PSW restart is initiated and causes the system
to kdump. The handling routine is always called with DAT turned
off. It then initializes the stack frame and invokes a callback.
The existing callbacks handle DAT as follows:
* __do_restart() and __machine_kexec() turn in on upon entry;
* __ipl_run(), __reipl_run() and __dump_run() do not turn it
right away, but all of them call diag308() - which turns DAT
on, but only if kasan is enabled;
In addition to the described complexity all callbacks (and the
functions they call) should avoid kasan instrumentation while
DAT is off.
This update enables DAT in the assembler restart handler and
relieves any callbacks (which are mostly C functions) from
dealing with DAT altogether.
There are four types of CPU restart that initialize control
registers in different ways:
1. Start of secondary CPU on boot - control registers are
inherited from the IPL CPU;
2. Restart of online CPU - control registers of the CPU being
restarted are kept;
3. Hotplug of offline CPU - control registers are inherited
from the starting CPU;
4. Start of offline CPU triggered by manual PSW restart -
the control registers are read from the absolute lowcore
and contain the boot time IPL CPU values updated with all
follow-up calls of smp_ctl_set_bit() and smp_ctl_clear_bit()
routines;
In first three cases contents of the control registers is the
most recent. In the latter case control registers are good
enough to facilitate successful completion of kdump operation.
Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This update partially reverts commit 3037a52f98 ("s390/nmi:
do register validation as early as possible").
Storage error checks and control registers validation are left
in the assembler code, since correct ASCEs and page tables are
required to enable DAT - which is done before the C handler is
entered.
System damage, kernel instruction address and PSW MWP checks
are left in the assembler code as well, since there is no way
to proceed if one of these checks is failed.
The getcpu vdso syscall reads CPU number from the programmable
field of the TOD clock. Disregard the TOD programmable register
validity bit and load the CPU number into the TOD programmable
field unconditionally.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
The current storage errors tackling is wrong - the DAT is
enabled in assembler code before the actual storage checks
in C half are executed. In case the page tables themselves
are damaged such approach is not going to work.
With this update unrecoverable storage errors are not
passed to C code for handling, but rather the machine
is stopped right away. The only exception to this flow
is when a machine check occurred in KVM guest - in this
case the errors are reinjected by the handler.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
The machine check handler must be entered with DAT disabled
in case control registers are corrupted or a storage error
happened and we can not tell if such error corresponds to a
page table.
Both of described conditions end up in stopping all CPUs and
entering the disabled wait in C half of the handler. However,
the storage errors are still checked after the DAT is enabled
and C code is entered. In case a page table is damaged such
flow is not expected to work.
This update paves the way for moving the storage error checks
from C to assembler half. All fatal errors that can only be
handled with DAT disabled are handled in assembler half also.
As result, the C half is only entered if the DAT is secured.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
In case of the !CONFIG_KVM use "jz" instead of "jnz" when
detecting user mode and get rid of unnecessary jump as result.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Christia Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Factor out SIEEXIT macro and use it instead of cleanup_sie
routine. As a side effect %r13 and %r14 are spared.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Christia Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
- Rework inline asm to get rid of error prone "register asm" constructs,
which are problematic especially when code instrumentation is enabled. In
particular introduce and use register pair union to allocate even/odd
register pairs. Unfortunately this breaks compatibility with older
clang compilers and minimum clang version for s390 has been raised to 13.
https://lore.kernel.org/linux-next/CAK7LNARuSmPCEy-ak0erPrPTgZdGVypBROFhtw+=3spoGoYsyw@mail.gmail.com/
- Fix gcc 11 warnings, which triggered various minor reworks all over
the code.
- Add zstd kernel image compression support.
- Rework boot CPU lowcore handling.
- De-duplicate and move kernel memory layout setup logic earlier.
- Few fixes in preparation for FORTIFY_SOURCE performing compile-time
and run-time field bounds checking for mem functions.
- Remove broken and unused power management support leftovers in s390
drivers.
- Disable stack-protector for decompressor and purgatory to fix buildroot
build.
- Fix vt220 sclp console name to match the char device name.
- Enable HAVE_IOREMAP_PROT and add zpci_set_irq()/zpci_clear_irq() in
zPCI code.
- Remove some implausible WARN_ON_ONCEs and remove arch specific counter
transaction call backs in favour of default transaction handling in
perf code.
- Extend/add new uevents for online/config/mode state changes of
AP card / queue device in zcrypt.
- Minor entry and ccwgroup code improvements.
- Other small various fixes and improvements all over the code.
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Merge tag 's390-5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Vasily Gorbik:
- Rework inline asm to get rid of error prone "register asm"
constructs, which are problematic especially when code
instrumentation is enabled.
In particular introduce and use register pair union to allocate
even/odd register pairs. Unfortunately this breaks compatibility with
older clang compilers and minimum clang version for s390 has been
raised to 13.
https://lore.kernel.org/linux-next/CAK7LNARuSmPCEy-ak0erPrPTgZdGVypBROFhtw+=3spoGoYsyw@mail.gmail.com/
- Fix gcc 11 warnings, which triggered various minor reworks all over
the code.
- Add zstd kernel image compression support.
- Rework boot CPU lowcore handling.
- De-duplicate and move kernel memory layout setup logic earlier.
- Few fixes in preparation for FORTIFY_SOURCE performing compile-time
and run-time field bounds checking for mem functions.
- Remove broken and unused power management support leftovers in s390
drivers.
- Disable stack-protector for decompressor and purgatory to fix
buildroot build.
- Fix vt220 sclp console name to match the char device name.
- Enable HAVE_IOREMAP_PROT and add zpci_set_irq()/zpci_clear_irq() in
zPCI code.
- Remove some implausible WARN_ON_ONCEs and remove arch specific
counter transaction call backs in favour of default transaction
handling in perf code.
- Extend/add new uevents for online/config/mode state changes of AP
card / queue device in zcrypt.
- Minor entry and ccwgroup code improvements.
- Other small various fixes and improvements all over the code.
* tag 's390-5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (91 commits)
s390/dasd: use register pair instead of register asm
s390/qdio: get rid of register asm
s390/ioasm: use symbolic names for asm operands
s390/ioasm: get rid of register asm
s390/cmf: get rid of register asm
s390/lib,string: get rid of register asm
s390/lib,uaccess: get rid of register asm
s390/string: get rid of register asm
s390/cmpxchg: use register pair instead of register asm
s390/mm,pages-states: get rid of register asm
s390/lib,xor: get rid of register asm
s390/timex: get rid of register asm
s390/hypfs: use register pair instead of register asm
s390/zcrypt: Switch to flexible array member
s390/speculation: Use statically initialized const for instructions
virtio/s390: get rid of open-coded kvm hypercall
s390/pci: add zpci_set_irq()/zpci_clear_irq()
scripts/min-tool-version.sh: Raise minimum clang version to 13.0.0 for s390
s390/ipl: use register pair instead of register asm
s390/mem_detect: fix tprot() program check new psw handling
...
The current irq entry code doesn't initialize pt_regs::flags. On exit to
user mode arch_do_signal_or_restart() tests whether PIF_SYSCALL is set,
which might yield wrong results.
Fix this by clearing pt_regs::flags in the entry.S irq handler
code.
Reported-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Fixes: 56e62a7370 ("s390: convert to generic entry")
Cc: <stable@vger.kernel.org> # 5.12
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Introduce OUTSIDE macro that checks whether an instruction
address is inside or outside of a block of instructions.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
cleanup_sie_mcck label is called from a single location only
and thus does not need to be a subroutine. Move the labelled
code to the caller - by doing that the SIE critical section
checks appear next to each other and the SIE cleanup becomes
bit more readable.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
arch/s390/kernel/syscall.c: In function __do_syscall:
arch/s390/kernel/syscall.c:147:9: warning: memcpy reading 64 bytes from a region of size 0 [-Wstringop-overread]
147 | memcpy(®s->gprs[8], S390_lowcore.save_area_sync, 8 * sizeof(unsigned long));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/s390/kernel/syscall.c:148:9: warning: memcpy reading 4 bytes from a region of size 0 [-Wstringop-overread]
148 | memcpy(®s->int_code, &S390_lowcore.svc_ilc, sizeof(regs->int_code));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix this by moving the gprs restore from C to assembly, and use a assignment
for int_code instead of memcpy.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Wrong condition check is used to decide if a machine check hit
while in KVM guest. As result of this check the instruction
following the SIE critical section might be considered as still
in KVM guest and _CIF_MCCK_GUEST CPU flag mistakenly set as
result.
Fixes: c929500d7a ("s390/nmi: s390: New low level handling for machine check happening in guest")
Cc: <stable@vger.kernel.org>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
The size of SIE critical section is calculated wrongly
as result of a missed subtraction in commit 0b0ed657fe
("s390: remove critical section cleanup from entry.S")
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Cc: <stable@vger.kernel.org>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Currently psw_idle does not allocate a stack frame and does not
save its r14 and r15 into the save area. Even though this is valid from
call ABI point of view, because psw_idle does not make any calls
explicitly, in reality psw_idle is an entry point for controlled
transition into serving interrupts. So, in practice, psw_idle stack
frame is analyzed during stack unwinding. Depending on build options
that r14 slot in the save area of psw_idle might either contain a value
saved by previous sibling call or complete garbage.
[task 0000038000003c28] do_ext_irq+0xd6/0x160
[task 0000038000003c78] ext_int_handler+0xba/0xe8
[task *0000038000003dd8] psw_idle_exit+0x0/0x8 <-- pt_regs
([task 0000038000003dd8] 0x0)
[task 0000038000003e10] default_idle_call+0x42/0x148
[task 0000038000003e30] do_idle+0xce/0x160
[task 0000038000003e70] cpu_startup_entry+0x36/0x40
[task 0000038000003ea0] arch_call_rest_init+0x76/0x80
So, to make a stacktrace nicer and actually point for the real caller of
psw_idle in this frequently occurring case, make psw_idle save its r14.
[task 0000038000003c28] do_ext_irq+0xd6/0x160
[task 0000038000003c78] ext_int_handler+0xba/0xe8
[task *0000038000003dd8] psw_idle_exit+0x0/0x6 <-- pt_regs
([task 0000038000003dd8] arch_cpu_idle+0x3c/0xd0)
[task 0000038000003e10] default_idle_call+0x42/0x148
[task 0000038000003e30] do_idle+0xce/0x160
[task 0000038000003e70] cpu_startup_entry+0x36/0x40
[task 0000038000003ea0] arch_call_rest_init+0x76/0x80
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Currently when interrupt arrives to cpu while in kernel context
INT_HANDLER macro (used for ext_int_handler and io_int_handler)
allocates new stack frame and pt_regs on the kernel stack and
sets up the backchain to jump over the pt_regs to the frame which has
been interrupted. This is not ideal to two reasons:
1. This hides the fact that kernel stack contains interrupt frame in it
and hence breaks arch_stack_walk_reliable(), which needs to know that to
guarantee "reliability" and checks that there are no pt_regs on the way.
2. It breaks the backchain unwinder logic, which assumes that the next
stack frame after an interrupt frame is reliable, while it is not.
In some cases (when r14 contains garbage) this leads to early unwinding
termination with an error, instead of marking frame as unreliable
and continuing.
To address that, only set backchain to 0.
Fixes: 56e62a7370 ("s390: convert to generic entry")
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
The current code uses the address in %r11 to figure out whether
it was called from the machine check handler or from a normal
interrupt handler. Instead of doing this implicit logic (which
is mostly a leftover from the old critical cleanup approach)
just add a second label and use that.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Instead of thrashing r11 which is normally our pointer to struct
pt_regs on the stack, use r13 as temporary register in the BR_EX
macro. r13 is already used in cleanup_sie, so no need to thrash
another register.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
If a machine check is coming in during sie, the PU saves the
control registers to the machine check save area. Afterwards
mcck_int_handler is called, which loads __LC_KERNEL_ASCE into
%cr1. Later the code restores %cr1 from the machine check area,
but that is wrong when SIE was interrupted because the machine
check area still contains the gmap asce. Instead it should return
with either __KERNEL_ASCE in %cr1 when interrupted in SIE or
the previous %cr1 content saved in the machine check save area.
Fixes: 87d5986345 ("s390/mm: remove set_fs / rework address space handling")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: <stable@kernel.org> # v5.8+
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
The previous code used the normal kernel stack for machine checks.
This is problematic when a machine check interrupts a system call
or interrupt handler right at the beginning where registers are set up.
Assume system_call is interrupted at the first instruction and a machine
check is triggered. The machine check handler is called, checks the PSW
to see whether it is coming from user space, notices that it is already
in kernel mode but %r15 still contains the user space stack. This would
lead to a kernel crash.
There are basically two ways of fixing that: Either using the 'critical
cleanup' approach which compares the address in the PSW to see whether
it is already at a point where the stack has been set up, or use an extra
stack for the machine check handler.
For simplicity, we will go with the second approach and allocate an extra
stack. This adds some memory overhead for large systems, but usually large
system have plenty of memory so this isn't really a concern. But it keeps
the mchk stack setup simple and less error prone.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: <stable@kernel.org> # v5.8+
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This is a preparation patch for two later bugfixes. In the past both
int_handler and machine check handler used SWITCH_KERNEL to switch to
the kernel stack. However, SWITCH_KERNEL doesn't work properly in machine
check context. So instead of adding more complexity to this macro, just
remove it.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: <stable@kernel.org> # v5.8+
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Use a cpu alternative to switch between stck and stckf instead of
making it compile time dependent. This will also make kernels compiled
for old machines, but running on newer machines, use stckf.
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.
There are a few special things on s390:
- PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't
know about our PIF flags in exit_to_user_mode_loop().
- The old code had several ways to restart syscalls:
a) PIF_SYSCALL_RESTART, which was only set during execve to force a
restart after upgrading a process (usually qemu-kvm) to pgste page
table extensions.
b) PIF_SYSCALL, which is set by do_signal() to indicate that the
current syscall should be restarted. This is changed so that
do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use
PIF_SYSCALL doesn't work with the generic code, and changing it
to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART
more unique.
- On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by
executing a svc instruction on the process stack which causes a fault.
While handling that fault the fault code sets PIF_SYSCALL to hand over
processing to the syscall code on exit to usermode.
The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets
a return value for a syscall. The s390x ptrace ABI uses r2 both for the
syscall number and return value, so ptrace cannot set the syscall number +
return value at the same time. The flag makes handling that a bit easier.
do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET
is set.
CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY.
CR1/7/13 will be checked both on kernel entry and exit to contain the
correct asces.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
that unwinding works properly.
- Fix stack unwinder test case to avoid rare interrupt stack corruption.
- Simplify udelay() and just let it busy loop instead of implementing a
complex logic.
- arch_cpu_idle() cleanup.
- Some other minor improvements.
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Merge tag 's390-5.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull more s390 updates from Heiko Carstens:
"This is mainly to decouple udelay() and arch_cpu_idle() and simplify
both of them.
Summary:
- Always initialize kernel stack backchain when entering the kernel,
so that unwinding works properly.
- Fix stack unwinder test case to avoid rare interrupt stack
corruption.
- Simplify udelay() and just let it busy loop instead of implementing
a complex logic.
- arch_cpu_idle() cleanup.
- Some other minor improvements"
* tag 's390-5.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
s390/zcrypt: convert comma to semicolon
s390/idle: allow arch_cpu_idle() to be kprobed
s390/idle: remove raw_local_irq_save()/restore() from arch_cpu_idle()
s390/idle: merge enabled_wait() and arch_cpu_idle()
s390/delay: remove udelay_simple()
s390/irq: select HAVE_IRQ_EXIT_ON_IRQ_STACK
s390/delay: simplify udelay
s390/test_unwind: use timer instead of udelay
s390/test_unwind: fix CALL_ON_STACK tests
s390: make calls to TRACE_IRQS_OFF/TRACE_IRQS_ON balanced
s390: always clear kernel stack backchain before calling functions
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Merge tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block
Pull TIF_NOTIFY_SIGNAL updates from Jens Axboe:
"This sits on top of of the core entry/exit and x86 entry branch from
the tip tree, which contains the generic and x86 parts of this work.
Here we convert the rest of the archs to support TIF_NOTIFY_SIGNAL.
With that done, we can get rid of JOBCTL_TASK_WORK from task_work and
signal.c, and also remove a deadlock work-around in io_uring around
knowing that signal based task_work waking is invoked with the sighand
wait queue head lock.
The motivation for this work is to decouple signal notify based
task_work, of which io_uring is a heavy user of, from sighand. The
sighand lock becomes a huge contention point, particularly for
threaded workloads where it's shared between threads. Even outside of
threaded applications it's slower than it needs to be.
Roman Gershman <romger@amazon.com> reported that his networked
workload dropped from 1.6M QPS at 80% CPU to 1.0M QPS at 100% CPU
after io_uring was changed to use TIF_NOTIFY_SIGNAL. The time was all
spent hammering on the sighand lock, showing 57% of the CPU time there
[1].
There are further cleanups possible on top of this. One example is
TIF_PATCH_PENDING, where a patch already exists to use
TIF_NOTIFY_SIGNAL instead. Hopefully this will also lead to more
consolidation, but the work stands on its own as well"
[1] https://github.com/axboe/liburing/issues/215
* tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block: (28 commits)
io_uring: remove 'twa_signal_ok' deadlock work-around
kernel: remove checking for TIF_NOTIFY_SIGNAL
signal: kill JOBCTL_TASK_WORK
io_uring: JOBCTL_TASK_WORK is no longer used by task_work
task_work: remove legacy TWA_SIGNAL path
sparc: add support for TIF_NOTIFY_SIGNAL
riscv: add support for TIF_NOTIFY_SIGNAL
nds32: add support for TIF_NOTIFY_SIGNAL
ia64: add support for TIF_NOTIFY_SIGNAL
h8300: add support for TIF_NOTIFY_SIGNAL
c6x: add support for TIF_NOTIFY_SIGNAL
alpha: add support for TIF_NOTIFY_SIGNAL
xtensa: add support for TIF_NOTIFY_SIGNAL
arm: add support for TIF_NOTIFY_SIGNAL
microblaze: add support for TIF_NOTIFY_SIGNAL
hexagon: add support for TIF_NOTIFY_SIGNAL
csky: add support for TIF_NOTIFY_SIGNAL
openrisc: add support for TIF_NOTIFY_SIGNAL
sh: add support for TIF_NOTIFY_SIGNAL
um: add support for TIF_NOTIFY_SIGNAL
...
udelay is implemented by using quite subtle details to make it
possible to load an idle psw and waiting for an interrupt even in irq
context or when interrupts are disabled. Also handling (or better: no
handling) of softirqs is taken into account.
All this is done to optimize for something which should in normal
circumstances never happen: calling udelay to busy wait. Therefore get
rid of the whole complexity and just busy loop like other
architectures are doing it also.
It could have been possible to use diag 0x44 instead of cpu_relax() in
the busy loop, however we have seen too many bad things happen with
diag 0x44 that it seems to be better to simply busy loop.
Also note that with this new implementation kernel preemption does
work when within the udelay loop. This did not work before.
To get a feeling what the former code optimizes for: IPL'ing a kernel
with 'defconfig' and afterwards compiling a kernel ends with a total
of zero udelay calls.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
In case of udelay CIF_IGNORE_IRQ is set. This leads to an unbalanced
call of TRACE_IRQS_OFF and TRACE_IRQS_ON. That is: from lockdep's
point of view TRACE_IRQS_ON is called one time too often.
This doesn't fix any real bug, just makes the calls balanced.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Clear the kernel stack backchain before potentially calling the
lockdep trace_hardirqs_off/on functions. Without this walking the
kernel backchain, e.g. during a panic, might stop too early.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
hugepages using CMA:
- Add arch_get_random_long() support.
- Add ap bus userspace notifications.
- Increase default size of vmalloc area to 512GB and otherwise let it increase
dynamically by the size of physical memory. This should fix all occurrences
where the vmalloc area was not large enough.
- Completely get rid of set_fs() (aka select SET_FS) and rework address space
handling while doing that; making address space handling much more simple.
- Reimplement getcpu vdso syscall in C.
- Add support for extended SCLP responses (> 4k). This allows e.g. to handle
also potential large system configurations.
- Simplify KASAN by removing 3-level page table support and only supporting
4-levels from now on.
- Improve debug-ability of the kernel decompressor code, which now prints also
stack traces and symbols in case of problems to the console.
- Remove more power management leftovers.
- Other various fixes and improvements all over the place.
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Merge tag 's390-5.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Heiko Carstens:
- Add support for the hugetlb_cma command line option to allocate
gigantic hugepages using CMA
- Add arch_get_random_long() support.
- Add ap bus userspace notifications.
- Increase default size of vmalloc area to 512GB and otherwise let it
increase dynamically by the size of physical memory. This should fix
all occurrences where the vmalloc area was not large enough.
- Completely get rid of set_fs() (aka select SET_FS) and rework address
space handling while doing that; making address space handling much
more simple.
- Reimplement getcpu vdso syscall in C.
- Add support for extended SCLP responses (> 4k). This allows e.g. to
handle also potential large system configurations.
- Simplify KASAN by removing 3-level page table support and only
supporting 4-levels from now on.
- Improve debug-ability of the kernel decompressor code, which now
prints also stack traces and symbols in case of problems to the
console.
- Remove more power management leftovers.
- Other various fixes and improvements all over the place.
* tag 's390-5.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (62 commits)
s390/mm: add support to allocate gigantic hugepages using CMA
s390/crypto: add arch_get_random_long() support
s390/smp: perform initial CPU reset also for SMT siblings
s390/mm: use invalid asce for user space when switching to init_mm
s390/idle: fix accounting with machine checks
s390/idle: add missing mt_cycles calculation
s390/boot: add build-id to decompressor
s390/kexec_file: fix diag308 subcode when loading crash kernel
s390/cio: fix use-after-free in ccw_device_destroy_console
s390/cio: remove pm support from ccw bus driver
s390/cio: remove pm support from css-bus driver
s390/cio: remove pm support from IO subchannel drivers
s390/cio: remove pm support from chsc subchannel driver
s390/vmur: remove unused pm related functions
s390/tape: remove unsupported PM functions
s390/cio: remove pm support from eadm-sch drivers
s390: remove pm support from console drivers
s390/dasd: remove unused pm related functions
s390/zfcp: remove pm support from zfcp driver
s390/ap: let bus_register() add the AP bus sysfs attributes
...
When a machine check interrupt is triggered during idle, the code
is using the async timer/clock for idle time calculation. It should use
the machine check enter timer/clock which is passed to the macro.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Cc: <stable@vger.kernel.org> # 5.8
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
During removal of the critical section cleanup the calculation
of mt_cycles during idle was removed. This causes invalid
accounting on systems with SMT enabled.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Cc: <stable@vger.kernel.org> # 5.8
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
With commit 58c644ba51 ("sched/idle: Fix arch_cpu_idle() vs
tracing") common code calls arch_cpu_idle() with a lockdep state that
tells irqs are on.
This doesn't work very well for s390: psw_idle() will enable interrupts
to wait for an interrupt. As soon as an interrupt occurs the interrupt
handler will verify if the old context was psw_idle(). If that is the
case the interrupt enablement bits in the old program status word will
be cleared.
A subsequent test in both the external as well as the io interrupt
handler checks if in the old context interrupts were enabled. Due to
the above patching of the old program status word it is assumed the
old context had interrupts disabled, and therefore a call to
TRACE_IRQS_OFF (aka trace_hardirqs_off_caller) is skipped. Which in
turn makes lockdep incorrectly "think" that interrupts are enabled
within the interrupt handler.
Fix this by unconditionally calling TRACE_IRQS_OFF when entering
interrupt handlers. Also call unconditionally TRACE_IRQS_ON when
leaving interrupts handlers.
This leaves the special psw_idle() case, which now returns with
interrupts disabled, but has an "irqs on" lockdep state. So callers of
psw_idle() must adjust the state on their own, if required. This is
currently only __udelay_disabled().
Fixes: 58c644ba51 ("sched/idle: Fix arch_cpu_idle() vs tracing")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Verify on exit to user space that always
- the primary ASCE (cr1) is set to kernel ASCE
- the secondary ASCE (cr7) is set to user ASCE
If this is not the case: panic since something went terribly wrong.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Remove set_fs support from s390. With doing this rework address space
handling and simplify it. As a result address spaces are now setup
like this:
CPU running in | %cr1 ASCE | %cr7 ASCE | %cr13 ASCE
----------------------------|-----------|-----------|-----------
user space | user | user | kernel
kernel, normal execution | kernel | user | kernel
kernel, kvm guest execution | gmap | user | kernel
To achieve this the getcpu vdso syscall is removed in order to avoid
secondary address mode and a separate vdso address space in for user
space. The getcpu vdso syscall will be implemented differently with a
subsequent patch.
The kernel accesses user space always via secondary address space.
This happens in different ways:
- with mvcos in home space mode and directly read/write to secondary
address space
- with mvcs/mvcp in primary space mode and copy from primary space to
secondary space or vice versa
- with e.g. cs in secondary space mode and access secondary space
Switching translation modes happens with sacf before and after
instructions which access user space, like before.
Lazy handling of control register reloading is removed in the hope to
make everything simpler, but at the cost of making kernel entry and
exit a bit slower. That is: on kernel entry the primary asce is always
changed to contain the kernel asce, and on kernel exit the primary
asce is changed again so it contains the user asce.
In kernel mode there is only one exception to the primary asce: when
kvm guests are executed the primary asce contains the gmap asce (which
describes the guest address space). The primary asce is reset to
kernel asce whenever kvm guest execution is interrupted, so that this
doesn't has to be taken into account for any user space accesses.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
We need to disable interrupts in load_fpu_regs(). Otherwise an
interrupt might come in after the registers are loaded, but before
CIF_FPU is cleared in load_fpu_regs(). When the interrupt returns,
CIF_FPU will be cleared and the registers will never be restored.
The entry.S code usually saves the interrupt state in __SF_EMPTY on the
stack when disabling/restoring interrupts. sie64a however saves the pointer
to the sie control block in __SF_SIE_CONTROL, which references the same
location. This is non-obvious to the reader. To avoid thrashing the sie
control block pointer in load_fpu_regs(), move the __SIE_* offsets eight
bytes after __SF_EMPTY on the stack.
Cc: <stable@vger.kernel.org> # 5.8
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Reported-by: Pierre Morel <pmorel@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
System call and program check handler both use the system call exit
path when returning to previous context. However the program check
handler jumps right to the end of the system call exit path if the
previous context is kernel context.
This lead to the quite odd double disabling of interrupts in the
system call exit path introduced with commit ce9dfafe29 ("s390:
fix system call exit path").
To avoid that have a separate program check handler exit path if the
previous context is kernel context.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
The system call exit path is running with interrupts enabled while
checking for TIF/PIF/CIF bits which require special handling. If all
bits have been checked interrupts are disabled and the kernel exits to
user space.
The problem is that after checking all bits and before interrupts are
disabled bits can be set already again, due to interrupt handling.
This means that the kernel can exit to user space with some
TIF/PIF/CIF bits set, which should never happen. E.g. TIF_NEED_RESCHED
might be set, which might lead to additional latencies, since that bit
will only be recognized with next exit to user space.
Fix this by checking the corresponding bits only when interrupts are
disabled.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Cc: <stable@vger.kernel.org> # 5.8
Acked-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Convert s390 to generic vDSO. There are a few special things on s390:
- vDSO can be called without a stack frame - glibc did this in the past.
So we need to allocate a stackframe on our own.
- The former assembly code used stcke to get the TOD clock and applied
time steering to it. We need to do the same in the new code. This is done
in the architecture specific __arch_get_hw_counter function. The steering
information is stored in an architecure specific area in the vDSO data.
- CPUCLOCK_VIRT is now handled with a syscall fallback, which might
be slower/less accurate than the old implementation.
The getcpu() function stays as an assembly function because there is no
generic implementation and the code is just a few lines.
Performance number from my system do 100 mio gettimeofday() calls:
Plain syscall: 8.6s
Generic VDSO: 1.3s
old ASM VDSO: 1s
So it's a bit slower but still much faster than syscalls.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
With the removal of the critical section cleanup, we now enter the svc
interrupt handler with interrupts disabled.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
When single stepping an svc instruction on s390, the kernel is entered
with a PER program check interruption. The program check handler than
jumps to the system call handler by reloading the PSW. The code didn't
set GPR13 to the thread pointer in struct task_struct. This made the
kernel access invalid memory while trying to fetch the syscall function
address. Fix this by always assigned GPR13 after .Lsysc_per.
Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
tracing expects to see invalid syscalls, so pass it through.
The syscall path in entry.S checks the syscall number before
looking up the handler, so it is still safe.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
The current code is rather complex and caused a lot of subtle
and hard to debug bugs in the past. Simplify the code by calling
the system_call handler with interrupts disabled, save
machine state, and re-enable them later.
This requires significant changes to the machine check handling code
as well. When the machine check interrupt arrived while being in kernel
mode the new code will signal pending machine checks with a SIGP external
call. When userspace was interrupted, the handler will switch to the
kernel stack and directly execute s390_handle_mcck().
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
When userspace executes a syscall or gets interrupted,
BEAR contains a kernel address when returning to userspace.
This make it pretty easy to figure out where the kernel is
mapped even with KASLR enabled. To fix this, add lpswe to
lowcore and always execute it there, so userspace sees only
the lowcore address of lpswe. For this we have to extend
both critical_cleanup and the SWITCH_ASYNC macro to also check
for lpswe addresses in lowcore.
Fixes: b2d24b97b2 ("s390/kernel: add support for kernel address space layout randomization (KASLR)")
Cc: <stable@vger.kernel.org> # v5.2+
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT.
Both PREEMPT and PREEMPT_RT require the same functionality which today
depends on CONFIG_PREEMPT.
Switch the preemption and entry code over to use CONFIG_PREEMPTION. Add
PREEMPT_RT output to die().
[bigeasy: +Kconfig, dumpstack.c]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Link: https://lore.kernel.org/r/20191015191821.11479-18-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There never have been distributions that shiped with CONFIG_SMP=n for
s390. In addition the kernel currently doesn't even compile with
CONFIG_SMP=n for s390. Most likely it wouldn't even work, even if we
fix the compile error, since nobody tests it, since there is no use
case that I can think of.
Therefore simply enforce CONFIG_SMP and get rid of some more or
less unused code.
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
The assembler code in arch/s390 misses proper ENDPROC statements
to properly end functions in a few places. Add them.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Alexander Gordeev
Heiko Carstens
Linus Torvalds
Sven Schnelle
Vasily Gorbik
Jens Axboe
Christian Borntraeger
Thomas Gleixner
Heiko Carstens
Martin Schwidefsky