[PATCH] kvm: fix hyperv tsc page clear wrong address

[Xiaoming Gao]

tsc page addr need clear the low HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT bits
before kvm_write_guest write the zero tsc_ref structure to guest, or it will lead
guest to get wrong clocksource.

windows guest will get strong impact, QueryPerformanceCounter will always return 0
,all things in windows rely on clock source will in serious chaos.

Signed-off-by: Xiaoming Gao <newtongao@xxxxxxxxxxx>
---
 arch/x86/kvm/x86.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f32a025..ed716cf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1898,6 +1898,7 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE))
 			break;
 		gfn = data >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
+		data &= ~((1 << HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT) - 1);
 		if (kvm_write_guest(kvm, data,
 			&tsc_ref, sizeof(tsc_ref)))
 			return 1;
-- 
1.7.1




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