Implement the SYNC_MMU capability for KVM MIPS, allowing changes in the
underlying user host virtual address (HVA) mappings to be promptly
reflected in the corresponding guest physical address (GPA) mappings.
This allows for several features to work with guest RAM which require
mappings to be altered or protected, such as copy-on-write, KSM (Kernel
Samepage Merging), idle page tracking, memory swapping, and guest memory
ballooning.
There are two main aspects of this change, described below.
The KVM MMU notifier architecture callbacks are implemented so we can be
notified of changes in the HVA mappings. These arrange for the guest
physical address (GPA) page tables to be modified and possibly for
derived mappings (GVA page tables and TLBs) to be flushed.
- kvm_unmap_hva[_range]() - These deal with HVA mappings being removed,
for example before a copy-on-write takes place, which requires the
corresponding GPA page table mappings to be removed too.
- kvm_set_spte_hva() - These update a GPA page table entry to match the
new HVA entry, but must be careful to respect KVM specific
configuration such as not dirtying a clean guest page which is dirty
to the host, and write protecting writable pages in read only
memslots (which will soon be supported).
- kvm[_test]_age_hva() - These update GPA page table entries to be old
(invalid) so that access can be tracked, making them young again.
The GPA page fault handling (kvm_mips_map_page) is updated to use
gfn_to_pfn_prot() (which may provide read-only pages), to handle
asynchronous page table invalidation from MMU notifier callbacks, and to
handle more cases in the fast path.
- mmu_notifier_seq is used to detect asynchronous page table
invalidations while we're holding a pfn from gfn_to_pfn_prot()
outside of kvm->mmu_lock, retrying if invalidations have taken place,
e.g. a COW or a KSM page merge.
- The fast path (_kvm_mips_map_page_fast) now handles marking old pages
as young / accessed, and disallowing dirtying of clean pages that
aren't actually writable (e.g. shared pages that should COW, and
read-only memory regions when they are enabled in a future patch).
- Due to the use of MMU notifications we no longer need to keep the
page references after we've updated the GPA page tables.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Propagate the GPA PTE protection bits on to the GVA PTEs on a mapped
fault (except _PAGE_WRITE, and filtered by the guest TLB entry), rather
than always overriding the protection. This allows dirty page tracking
to work in mapped guest segments as a clear dirty bit in the GPA PTE
will propagate to the GVA PTEs even when the guest TLB has the dirty bit
set.
Since the filtering of protection bits is now abstracted, if the buddy
GVA PTE is also valid, we obtain the corresponding GPA PTE using a
simple non-allocating walk and load that into the GVA PTE similarly
(which may itself be invalid).
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Propagate the GPA PTE protection bits on to the GVA PTEs on a KSeg0
fault (except _PAGE_WRITE), rather than always overriding the
protection. This allows dirty page tracking to work in KSeg0 as a clear
dirty bit in the GPA PTE will propagate to the GVA PTEs.
This makes it simpler to use a single kvm_mips_map_page() to obtain both
the main GPA PTE and its buddy (which may be invalid), which also allows
memory regions to be fully accessible when they don't start and end on a
2*PAGE_SIZE boundary.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Update kvm_mips_map_page() to handle logging of dirty guest physical
pages. Upcoming patches will propagate the dirty bit to the GVA page
tables.
A fast path is added for handling protection bits that can be resolved
without calling into KVM, currently just dirtying of clean pages being
written to.
The slow path marks the GPA page table entry writable only on writes,
and at the same time marks the page dirty in the dirty page logging
bitmask.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
When an existing memory region has dirty page logging enabled, make the
entire slot clean (read only) so that writes will immediately start
logging dirty pages (once the dirty bit is transferred from GPA to GVA
page tables in an upcoming patch).
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
MIPS hasn't up to this point properly supported dirty page logging, as
pages in slots with dirty logging enabled aren't made clean, and tlbmod
exceptions from writes to clean pages have been assumed to be due to
guest TLB protection and unconditionally passed to the guest.
Use the generic dirty logging helper kvm_get_dirty_log_protect() to
properly implement kvm_vm_ioctl_get_dirty_log(), similar to how ARM
does. This uses xchg to clear the dirty bits when reading them, rather
than wiping them out afterwards with a memset, which would potentially
wipe recently set bits that weren't caught by kvm_get_dirty_log(). It
also makes the pages clean again using the
kvm_arch_mmu_enable_log_dirty_pt_masked() architecture callback so that
further writes after the shadow memslot is flushed will trigger tlbmod
exceptions and dirty handling.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Add a helper function to make a range of guest physical address (GPA)
mappings in the GPA page table clean so that writes can be caught. This
will be used in a few places to manage dirty page logging.
Note that until the dirty bit is transferred from GPA page table entries
to GVA page table entries in an upcoming patch this won't trigger a TLB
modified exception on write.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Rewrite TLB modified exception handling to handle read only GPA memory
regions, instead of unconditionally passing the exception to the guest.
If the guest TLB is not the cause of the exception we call into the
normal TLB fault handling depending on the memory segment, which will
soon attempt to remap the physical page to be writable (handling dirty
page tracking or copy on write in the process).
Failing that we fall back to treating it as MMIO, due to a read only
memory region. Once the capability is enabled, this will allow read only
memory regions (such as the Malta boot flash as emulated by QEMU) to
have writes treated as MMIO, while still allowing reads to run
untrapped.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Treat unhandled accesses to guest KSeg0 as MMIO, rather than only host
KSeg0 addresses. This will allow read only memory regions (such as the
Malta boot flash as emulated by QEMU) to have writes (before reads)
treated as MMIO, and unallocated physical addresses to have all accesses
treated as MMIO.
The MMIO emulation uses the gva_to_gpa callback, so this is also updated
for trap & emulate to handle guest KSeg0 addresses.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Abstract the handling of bad guest loads and stores which may need to
trigger an MMIO, so that the same code can be used in a later patch for
guest KSeg0 addresses (TLB exception handling) as well as for host KSeg1
addresses (existing address error exception and TLB exception handling).
We now use kvm_mips_emulate_store() and kvm_mips_emulate_load() directly
rather than the more generic kvm_mips_emulate_inst(), as there is no
need to expose emulation of any other instructions.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
kvm_mips_map_page() will need to know whether the fault was due to a
read or a write in order to support dirty page tracking,
KVM_CAP_SYNC_MMU, and read only memory regions, so get that information
passed down to it via new bool write_fault arguments to various
functions.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Ignore userland writes to CP0_Config7 rather than reporting an error,
since we do allow reads of this register and it is claimed to exist in
the ioctl API.
This allows userland to blindly save and restore KVM registers without
having to special case certain registers as not being writable, for
example during live migration once dirty page logging is fixed.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Implement the kvm_arch_flush_shadow_all() and
kvm_arch_flush_shadow_memslot() KVM functions for MIPS to allow guest
physical mappings to be safely changed.
The general MIPS KVM code takes care of flushing of GPA page table
entries. kvm_arch_flush_shadow_all() flushes the whole GPA page table,
and is always called on the cleanup path so there is no need to acquire
the kvm->mmu_lock. kvm_arch_flush_shadow_memslot() flushes only the
range of mappings in the GPA page table corresponding to the slot being
flushed, and happens when memory regions are moved or deleted.
MIPS KVM implementation callbacks are added for handling the
implementation specific flushing of mappings derived from the GPA page
tables. These are implemented for trap_emul.c using
kvm_flush_remote_tlbs() which should now be functional, and will flush
the per-VCPU GVA page tables and ASIDS synchronously (before next
entering guest mode or directly accessing GVA space).
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Use the lockless GVA helpers to implement the reading of guest
instructions for emulation. This will allow it to handle asynchronous
TLB flushes when they are implemented.
This is a little more complicated than the other two cases (get_inst()
and dynamic translation) due to the need to emulate the appropriate
guest TLB exception when the address isn't present or isn't valid in the
guest TLB.
Since there are several protected cache ops that may need to be
performed safely, this is abstracted by kvm_mips_guest_cache_op() which
is passed a protected cache op function pointer and takes care of the
lockless operation and fault handling / retry if the op should fail,
taking advantage of the new errors which the protected cache ops can now
return. This allows the existing advance fault handling which relied on
host TLB lookups to be removed, along with the now unused
kvm_mips_host_tlb_lookup(),
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Use the lockless GVA helpers to implement the reading of guest
instructions for emulation. This will allow it to handle asynchronous
TLB flushes when they are implemented.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Use the lockless GVA helpers to implement the dynamic translation of
guest instructions. This will allow it to handle asynchronous TLB
flushes when they are implemented.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Add helpers to allow for lockless direct access to the GVA space, by
changing the VCPU mode to READING_SHADOW_PAGE_TABLES for the duration of
the access. This allows asynchronous TLB flush requests in future
patches to safely trigger either a TLB flush before the direct GVA space
access, or a delay until the in-progress lockless direct access is
complete.
The kvm_trap_emul_gva_lockless_begin() and
kvm_trap_emul_gva_lockless_end() helpers take care of guarding the
direct GVA accesses, and kvm_trap_emul_gva_fault() tries to handle a
uaccess fault resulting from a flush having taken place.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
The stale ASID checks taking place on VCPU load can be reduced:
- Now that we check for a stale ASID on guest re-entry, there is no need
to do so when loading the VCPU outside of guest context, since it will
happen before entering the guest. Note that a lot of KVM VCPU ioctls
will cause the VCPU to be loaded but guest context won't be entered.
- There is no need to check for a stale kernel_mm ASID when the guest is
in user mode and vice versa. In fact doing so can potentially be
problematic since the user_mm ASID regeneration may trigger a new ASID
cycle, which would cause the kern_mm ASID to become stale after it has
been checked for staleness.
Therefore only check the ASID for the mm corresponding to the current
guest mode, and only if we're already in guest context. We drop some of
the related kvm_debug() calls here too.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Add handling of TLB invalidation requests before entering guest mode.
This will allow asynchonous invalidation of the VCPU mappings when
physical memory regions are altered. Should the CPU running the VCPU
already be in guest mode an IPI will be sent to trigger a guest exit.
The reload_asid path will be used in a future patch for when GVA is
about to be directly accessed by KVM.
In the process, the stale user ASID check in the re-entry path (for lazy
user GVA flushing) is generalised to check the ASID for the current
guest mode, in case a TLB invalidation request was handled. This has the
side effect of making the ASID checks on vcpu_load too conservative,
which will be addressed in a later patch.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Keep the vcpu->mode and vcpu->cpu variables up to date so that
kvm_make_all_cpus_request() has a chance of functioning correctly. This
will soon need to be used for kvm_flush_remote_tlbs().
We can easily update vcpu->cpu when the VCPU context is loaded or saved,
which will happen when accessing guest context and when the guest is
scheduled in and out.
We need to be a little careful with vcpu->mode though, as we will in
future be checking for outstanding VCPU requests, and this must be done
after the value of IN_GUEST_MODE in vcpu->mode is visible to other CPUs.
Otherwise the other CPU could fail to trigger an IPI to wait for
completion dispite the VCPU request not being seen.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Current guest physical memory is mapped to host physical addresses using
a single linear array (guest_pmap of length guest_pmap_npages). This was
only really meant to be temporary, and isn't sparse, so its wasteful of
memory. A small amount of RAM at GPA 0 and a small boot exception vector
at GPA 0x1fc00000 cannot be represented without a full 128KiB guest_pmap
allocation (MIPS32 with 16KiB pages), which is one reason why QEMU
currently runs its boot code at the top of RAM instead of the usual boot
exception vector address.
Instead use the existing infrastructure for host virtual page table
management to allocate a page table for guest physical memory too. This
should be sufficient for now, assuming the size of physical memory
doesn't exceed the size of virtual memory. It may need extending in
future to handle XPA (eXtended Physical Addressing) in 32-bit guests, as
supported by VZ guests on P5600.
Some of this code is based loosely on Cavium's VZ KVM implementation.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
When exiting from the guest, store the values of the CP0_BadInstr and
CP0_BadInstrP registers if they exist, which contain the encodings of
the instructions which caused the last synchronous exception.
When the instruction is needed for emulation, kvm_get_badinstr() and
kvm_get_badinstrp() are used instead of calling kvm_get_inst() directly,
to decide whether to read the saved CP0_BadInstr/CP0_BadInstrP registers
(if they exist), or read the instruction from memory (if not).
The use of these registers should be more robust than using
kvm_get_inst(), as it actually gives the instruction encoding seen by
the hardware rather than relying on user accessors after the fact, which
can be fooled by incoherent icache or a racing code modification. It
will also work with VZ, where the guest virtual memory isn't directly
accessible by the host with user accessors.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Currently kvm_get_inst() returns KVM_INVALID_INST in the event of a
fault reading the guest instruction. This has the rather arbitrary magic
value 0xdeadbeef. This API isn't very robust, and in fact 0xdeadbeef is
a valid MIPS64 instruction encoding, namely "ld t1,-16657(s5)".
Therefore change the kvm_get_inst() API to return 0 or -EFAULT, and to
return the instruction via a u32 *out argument. We can then drop the
KVM_INVALID_INST definition entirely.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
In order to make use of the CP0_BadInstr & CP0_BadInstrP registers we
need to be a bit more careful not to treat code fetch faults as MMIO,
lest we hit an UNPREDICTABLE register value when we try to emulate the
MMIO load instruction but there was no valid instruction word available
to the hardware.
Add a kvm_is_ifetch_fault() helper to try to figure out whether a load
fault was due to a code fetch, and prevent MMIO instruction emulation in
that case.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
MIPS KVM uses its own variation of get_new_mmu_context() which takes an
extra vcpu pointer (unused) and does exactly the same thing.
Switch to just using get_new_mmu_context() directly and drop KVM's
version of it as it doesn't really serve any purpose.
The nearby declarations of kvm_mips_alloc_new_mmu_context(),
kvm_mips_vcpu_load() and kvm_mips_vcpu_put() are also removed from
kvm_host.h, as no definitions or users exist.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
When exceptions are injected into the MIPS KVM guest, the whole host TLB
is flushed (except any entries in the guest KSeg0 range). This is
certainly not mandated by the architecture when exceptions are taken
(userland can't directly change TLB mappings anyway), and is a pretty
heavyweight operation:
- There may be hundreds of TLB entries especially when a 512 entry FTLB
is present. These are walked and read and conditionally invalidated,
so the TLBINV feature can't be used either.
- It'll indiscriminately wipe out entries belonging to other memory
spaces. A simple ASID regeneration would be much faster to perform,
although it'd wipe out the guest KSeg0 mappings too.
My suspicion is that this was simply to plaster over the fact that
kvm_mips_host_tlb_inv() incorrectly only invalidated TLB entries in the
ASID for guest usermode, and not the ASID for guest kernelmode.
Now that the recent commit "KVM: MIPS/TLB: Flush host TLB entry in
kernel ASID" fixes kvm_mips_host_tlb_inv() to flush TLB entries in the
kernelmode ASID when the guest TLB changes, lets drop these calls and
the otherwise unused kvm_mips_flush_host_tlb().
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that KVM no longer uses wired entries we can safely use
local_flush_tlb_all() when we need to flush the entire TLB (on the start
of a new ASID cycle). This doesn't flush wired entries, which allows
other code to use them without KVM clobbering them all the time. It also
is more up to date, knowing about the tlbinv architectural feature,
flushing of micro TLB on cores where that is necessary (Loongson I
believe), and knows to stop the HTW while doing so.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Use protected_writeback_dcache_line() instead of flush_dcache_line(),
and protected_flush_icache_line() instead of flush_icache_line(), so
that CACHEE (the EVA variant) is used on EVA host kernels.
Without this, guest floating point branch delay slot emulation via a
trampoline on the user stack fails on EVA host kernels due to failure of
the icache sync, resulting in the break instruction getting skipped and
execution from the stack.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that we have GVA page tables, use standard user accesses with page
faults disabled to read & modify guest instructions. This should be more
robust (than the rather dodgy method of accessing guest mapped segments
by just directly addressing them) and will also work with Enhanced
Virtual Addressing (EVA) host kernel configurations where dedicated
instructions are needed for accessing user mode memory.
For simplicity and speed we do this regardless of the guest segment the
address resides in, rather than handling guest KSeg0 specially with
kmap_atomic() as before.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that the commpage doesn't use wired TLB entries, the per-CPU
vm_init() callback is the only work done by kvm_mips_init_vm_percpu().
The trap & emulate implementation doesn't actually need to do anything
from vm_init(), and the future VZ implementation would be better served
by a kvm_arch_hardware_enable callback anyway.
Therefore drop the vm_init() callback entirely, allowing the
kvm_mips_init_vm_percpu() function to also be dropped, along with the
kvm_mips_instance atomic counter.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that we have GVA page tables and an optimised TLB refill handler in
place, convert the handling of commpage faults from the guest kernel to
fill the GVA page table and invalidate the TLB entry, rather than
filling the wired TLB entry directly.
For simplicity we no longer use a wired entry for the commpage (refill
should be much cheaper with the fast-path handler anyway). Since we
don't need to manipulate the TLB directly any longer, move the function
from tlb.c to mmu.c. This puts it closer to the similar functions
handling KSeg0 and TLB mapped page faults from the guest.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that we have GVA page tables and an optimised TLB refill handler in
place, convert the handling of page faults in TLB mapped segment from
the guest to fill a single GVA page table entry and invalidate the TLB
entry, rather than filling a TLB entry pair directly.
Also remove the now unused kvm_mips_get_{kernel,user}_asid() functions
in mmu.c and kvm_mips_host_tlb_write() in tlb.c.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Now that we have GVA page tables and an optimised TLB refill handler in
place, convert the handling of KSeg0 page faults from the guest to fill
the GVA page tables and invalidate the TLB entry, rather than filling a
TLB entry directly.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Implement invalidation of specific pairs of GVA page table entries in
one or both of the GVA page tables. This is used when existing mappings
are replaced in the guest TLB by emulated TLBWI/TLBWR instructions. Due
to the sharing of page tables in the host kernel range, we should be
careful not to allow host pages to be invalidated.
Add a helper kvm_mips_walk_pgd() which can be used when walking of
either GPA (future patches) or GVA page tables is needed, optionally
with allocation of page tables along the way when they don't exist.
GPA page table walking will need to be protected by the kvm->mmu_lock,
so we also add a small MMU page cache in each KVM VCPU, like that found
for other architectures but smaller. This allows enough pages to be
pre-allocated to handle a single fault without holding the lock,
allowing the helper to run with the lock held without having to handle
allocation failures.
Using the same mechanism for GVA allows the same code to be used, and
allows it to use the same cache of allocated pages if the GPA walk
didn't need to allocate any new tables.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Implement invalidation of large ranges of virtual addresses from GVA
page tables in response to a guest ASID change (immediately for guest
kernel page table, lazily for guest user page table).
We iterate through a range of page tables invalidating entries and
freeing fully invalidated tables. To minimise overhead the exact ranges
invalidated depends on the flags argument to kvm_mips_flush_gva_pt(),
which also allows it to be used in future KVM_CAP_SYNC_MMU patches in
response to GPA changes, which unlike guest TLB mapping changes affects
guest KSeg0 mappings.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Refactor kvm_mips_host_tlb_inv() to also be able to invalidate any
matching TLB entry in the kernel ASID rather than assuming only the TLB
entries in the user ASID can change. Two new bool user/kernel arguments
allow the caller to indicate whether the mapping should affect each of
the ASIDs for guest user/kernel mode.
- kvm_mips_invalidate_guest_tlb() (used by TLBWI/TLBWR emulation) can
now invalidate any corresponding TLB entry in both the kernel ASID
(guest kernel may have accessed any guest mapping), and the user ASID
if the entry being replaced is in guest USeg (where guest user may
also have accessed it).
- The tlbmod fault handler (and the KSeg0 / TLB mapped / commpage fault
handlers in later patches) can now invalidate the corresponding TLB
entry in whichever ASID is currently active, since only a single page
table will have been updated anyway.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
kvm_mips_host_tlb_inv() uses the TLBP instruction to probe the host TLB
for an entry matching the given guest virtual address, and determines
whether a match was found based on whether CP0_Index > 0. This is
technically incorrect as an index of 0 (with the high bit clear) is a
perfectly valid TLB index.
This is harmless at the moment due to the use of at least 1 wired TLB
entry for the KVM commpage, however we will soon be ridding ourselves of
that particular wired entry so lets fix the condition in case the entry
needing invalidation does land at TLB index 0.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Use functions from the general MIPS TLB exception vector generation code
(tlbex.c) to construct a fast path TLB refill handler similar to the
general one, but cut down and capable of preserving K0 and K1.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
tlbex.c uses the implementation dependent $22 CP0 register group on
NetLogic cores, with the help of the c0_kscratch() helper. Allow these
registers to be allocated by the KVM entry code too instead of assuming
KScratch registers are all $31, which will also allow pgd_reg to be
handled since it is allocated that way.
We also drop the masking of kscratch_mask with 0xfc, as it is redundant
for the standard KScratch registers (Config4.KScrExist won't have the
low 2 bits set anyway), and apparently not necessary for NetLogic.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Activate the GVA page tables when in guest context. This will allow the
normal Linux TLB refill handler to fill from it when guest memory is
read, as well as preventing accidental reading from user memory.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Allocate GVA -> HPA page tables for guest kernel and guest user mode on
each VCPU, to allow for fast path TLB refill handling to be added later.
In the process kvm_arch_vcpu_init() needs updating to pass on any error
from the vcpu_init() callback.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Wire up a vcpu uninit implementation callback. This will be used for the
clean up of GVA->HPA page tables.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Set init_mm as the active_mm and update mm_cpumask(current->mm) to
reflect that it isn't active when in guest context. This prevents cache
management code from attempting cache flushes on host virtual addresses
while in guest context, for example due to a cache management IPIs or
later when writing of dynamically translated code hits copy on write.
We do this using helpers in static kernel code to avoid having to export
init_mm to modules.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
We only need the guest ASID loaded while in guest context, i.e. while
running guest code and while handling guest exits. We load the guest
ASID when entering the guest, however we restore the host ASID later
than necessary, when the VCPU state is saved i.e. vcpu_put() or slightly
earlier if preempted after returning to the host.
This mismatch is both unpleasant and causes redundant host ASID restores
in kvm_trap_emul_vcpu_put(). Lets explicitly restore the host ASID when
returning to the host, and don't bother restoring the host ASID on
context switch in unless we're already in guest context.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Add implementation callbacks for entering the guest (vcpu_run()) and
reentering the guest (vcpu_reenter()), allowing implementation specific
operations to be performed before entering the guest or after returning
to the host without cluttering kvm_arch_vcpu_ioctl_run().
This allows the T&E specific lazy user GVA flush to be moved into
trap_emul.c, along with disabling of the HTW. We also move
kvm_mips_deliver_interrupts() as VZ will need to restore the guest timer
state prior to delivering interrupts.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
The kvm_vcpu_arch structure contains both mm_structs for allocating MMU
contexts (primarily the ASID) but it also copies the resulting ASIDs
into guest_{user,kernel}_asid[] arrays which are referenced from uasm
generated code.
This duplication doesn't seem to serve any purpose, and it gets in the
way of generalising the ASID handling across guest kernel/user modes, so
lets just extract the ASID straight out of the mm_struct on demand, and
in fact there are convenient cpu_context() and cpu_asid() macros for
doing so.
To reduce the verbosity of this code we do also add kern_mm and user_mm
local variables where the kernel and user mm_structs are used.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
The MIPS KVM host and guest GVA ASIDs may need regenerating when
scheduling a process in guest context, which is done from the
kvm_arch_vcpu_load() / kvm_arch_vcpu_put() functions in mmu.c.
However this is a fairly implementation specific detail. VZ for example
may use GuestIDs instead of normal ASIDs to distinguish mappings
belonging to different guests, and even on VZ without GuestID the root
TLB will be used differently to trap & emulate.
Trap & emulate GVA ASIDs only relate to the user part of the full
address space, so can be left active during guest exit handling (guest
context) to allow guest instructions to be easily read and translated.
VZ root ASIDs however are for GPA mappings so can't be left active
during normal kernel code. They also aren't useful for accessing guest
virtual memory, and we should have CP0_BadInstr[P] registers available
to provide encodings of trapping guest instructions anyway.
Therefore move the ASID preemption handling into the implementation
callback.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Convert the get_regs() and set_regs() callbacks to vcpu_load() and
vcpu_put(), which provide a cpu argument and more closely match the
kvm_arch_vcpu_load() / kvm_arch_vcpu_put() that they are called by.
This is in preparation for moving ASID management into the
implementations.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
KVM T&E uses an ASID for guest kernel mode and an ASID for guest user
mode. The current ASID is saved when the guest is scheduled out, and
restored when scheduling back in, with checks for whether the ASID needs
to be regenerated.
This isn't really necessary as the ASID can be easily determined by the
current guest mode, so lets simplify it to just read the required ASID
from guest_kernel_asid or guest_user_asid even if the ASID hasn't been
regenerated.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
MIPS incompletely implements the KVM_NMI ioctl to supposedly perform a
CPU reset, but all it actually does is invalidate the ASIDs. It doesn't
expose the KVM_CAP_USER_NMI capability which is supposed to indicate the
presence of the KVM_NMI ioctl, and no user software actually uses it on
MIPS.
Since this is dead code that would technically need updating for GVA
page table handling in upcoming patches, remove it now. If we wanted to
implement NMI injection later it can always be done properly along with
the KVM_CAP_USER_NMI capability, and if we wanted to implement a proper
CPU reset it would be better done with a separate ioctl.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
James Hogan