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authorVitaly Kuznetsov <vkuznets@redhat.com>2019-04-03 19:03:09 +0200
committerIngo Molnar <mingo@kernel.org>2019-04-16 12:28:23 +0200
commitba696429d290690db967e5f49463df4b2c1314a4 (patch)
tree2ab43dcb4eb5e5139d623dcc069735dea6479297 /arch/x86/hyperv
parent618d919cae2fcaadc752f27ddac8b939da8b441a (diff)
downloadlinux-ba696429d290690db967e5f49463df4b2c1314a4.tar.bz2
x86/hyper-v: Implement EOI assist
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>
Diffstat (limited to 'arch/x86/hyperv')
-rw-r--r--arch/x86/hyperv/hv_apic.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index 8eb6fbee8e13..5c056b8aebef 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -86,6 +86,11 @@ static void hv_apic_write(u32 reg, u32 val)
static void hv_apic_eoi_write(u32 reg, u32 val)
{
+ struct hv_vp_assist_page *hvp = hv_vp_assist_page[smp_processor_id()];
+
+ if (hvp && (xchg(&hvp->apic_assist, 0) & 0x1))
+ return;
+
wrmsr(HV_X64_MSR_EOI, val, 0);
}