__send_ipi_mask_ex() uses an optimization: when the target CPU mask is
equal to 'cpu_present_mask' it uses 'HV_GENERIC_SET_ALL' format to avoid
converting the specified cpumask to VP_SET. This case was overlooked when
'exclude_self' parameter was added. As the result, a spurious IPI to
'self' can be send.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Fixes: dfb5c1e12c ("x86/hyperv: remove on-stack cpumask from hv_send_ipi_mask_allbutself")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20211006125016.941616-1-vkuznets@redhat.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
It is not a good practice to allocate a cpumask on stack, given it may
consume up to 1 kilobytes of stack space if the kernel is configured to
have 8192 cpus.
The internal helper functions __send_ipi_mask{,_ex} need to loop over
the provided mask anyway, so it is not too difficult to skip `self'
there. We can thus do away with the on-stack cpumask in
hv_send_ipi_mask_allbutself.
Adjust call sites of __send_ipi_mask as needed.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Michael Kelley <mikelley@microsoft.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 68bb7bfb79 ("X86/Hyper-V: Enable IPI enlightenments")
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210910185714.299411-3-wei.liu@kernel.org
There is not a consistent pattern for checking Hyper-V hypercall status.
Existing code uses a number of variants. The variants work, but a consistent
pattern would improve the readability of the code, and be more conformant
to what the Hyper-V TLFS says about hypercall status.
Implemented new helper functions hv_result(), hv_result_success(), and
hv_repcomp(). Changed the places where hv_do_hypercall() and related variants
are used to use the helper functions.
Signed-off-by: Joseph Salisbury <joseph.salisbury@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1618620183-9967-2-git-send-email-joseph.salisbury@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Fixes the following W=1 kernel build warning(s):
arch/x86/hyperv/hv_apic.c:58:15: warning: variable ‘hi’ set but not used [-Wunused-but-set-variable]
Compiled with CONFIG_HYPERV enabled:
make allmodconfig ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
make W=1 arch/x86/hyperv/hv_apic.o ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
HV_X64_MSR_EOI occupies bit 31:0 and HV_X64_MSR_TPR occupies bit 7:0,
which means the higher 32 bits are not really used. Cast the variable hi
to void to silence this warning.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xu Yihang <xuyihang@huawei.com>
Link: https://lore.kernel.org/r/20210323025013.191533-1-xuyihang@huawei.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
The comment about Hyper-V accessors is unclear regarding their
potential use in x2apic mode, as is the associated commit message
in e211288b72. Clarify that while the architectural and
synthetic MSRs are equivalent in x2apic mode, the full set of xapic
accessors cannot be used because of register layout differences.
Fixes: e211288b72 ("x86/hyperv: Make vapic support x2apic mode")
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1603723972-81303-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
When sending an IPI to a single CPU there is no need to deal with cpumasks.
With 2 CPU guest on WS2019 a minor (like 3%, 8043 -> 7761 CPU cycles)
improvement with smp_call_function_single() loop benchmark can be seeb. The
optimization, however, is tiny and straitforward. Also, send_ipi_one() is
important for PV spinlock kick.
Switching to the regular APIC IPI send for CPU > 64 case does not make
sense as it is twice as expesive (12650 CPU cycles for __send_ipi_mask_ex()
call, 26000 for orig_apic.send_IPI(cpu, vector)).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Link: https://lkml.kernel.org/r/20191027151938.7296-1-vkuznets@redhat.com
Now that there's Hyper-V IOMMU driver, Linux can switch to x2apic mode
when supported by the vcpus.
However, the apic access functions for Hyper-V enlightened apic assume
xapic mode only.
As a result, Linux fails to bring up secondary cpus when run as a guest
in QEMU/KVM with both hv_apic and x2apic enabled.
According to Michael Kelley, when in x2apic mode, the Hyper-V synthetic
apic MSRs behave exactly the same as the corresponding architectural
x2apic MSRs, so there's no need to override the apic accessors. The
only exception is hv_apic_eoi_write, which benefits from lazy EOI when
available; however, its implementation works for both xapic and x2apic
modes.
Fixes: 29217a4746 ("iommu/hyper-v: Add Hyper-V stub IOMMU driver")
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20191010123258.16919-1-rkagan@virtuozzo.com
Hyper-V TLFS suggests an optimization to avoid imminent VMExit on EOI:
"The OS performs an EOI by atomically writing zero to the EOI Assist field
of the virtual VP assist page and checking whether the "No EOI required"
field was previously zero. If it was, the OS must write to the
HV_X64_APIC_EOI MSR thereby triggering an intercept into the hypervisor."
Implement the optimization in Linux.
Tested-by: Long Li <longli@microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Simon Xiao <sixiao@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-hyperv@vger.kernel.org
Link: http://lkml.kernel.org/r/20190403170309.4107-1-vkuznets@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
These structures are going to be used from KVM code so let's make
their names reflect their Hyper-V origin.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When there is no need to send an IPI to a CPU with VP number > 64
we can do the job with fast HVCALL_SEND_IPI hypercall.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Link: https://lkml.kernel.org/r/20180622170625.30688-4-vkuznets@redhat.com
Current Hyper-V TLFS (v5.0b) claims that HvCallSendSyntheticClusterIpi
hypercall can't be 'fast' (passing parameters through registers) but
apparently this is not true, Windows always uses 'fast' version. We can
do the same in Linux too.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Link: https://lkml.kernel.org/r/20180622170625.30688-3-vkuznets@redhat.com
The Hyper-V APIC code is built when CONFIG_HYPERV is enabled but the actual
code in that file is guarded with CONFIG_X86_64. There is no point in doing
this. Neither is there a point in having the CONFIG_HYPERV guard in there
because the containing directory is not built when CONFIG_HYPERV=n.
Further for the hv_init_apic() function a stub is provided only for
CONFIG_HYPERV=n, which is pointless as the callsite is not compiled at
all. But for X86_32 the stub is missing and the build fails.
Clean that up:
- Compile hv_apic.c only when CONFIG_X86_64=y
- Make the stub for hv_init_apic() available when CONFG_X86_64=n
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Not all configurations magically include asm/apic.h, but the Hyper-V code
requires it. Include it explicitely.
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Vitaly Kuznetsov
Wei Liu
Joseph Salisbury
Xu Yihang
Michael Kelley
Thomas Gleixner
Roman Kagan
YueHaibing
K. Y. Srinivasan