Re: [patch NOT added to the 3.12 stable tree] kvm: fix wrong address when writing Hyper-V tsc page

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Il 17/07/2014 15:11, Jiri Slaby ha scritto:
From: Xiaoming Gao <newtongao@xxxxxxxxxxx>

This patch does NOT apply to the 3.12 stable tree. If you still want
it applied, please provide a backport.

The bug does not affect Linux v3.13 and earlier.

Thanks,

Paolo

===============

commit e1fa108d24697b78348fd4e5a531029a50d0d36d upstream.

When kvm_write_guest writes the tsc_ref structure to the guest, or it will lead
the low HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT bits of the TSC page address
must be cleared, or the guest can see a non-zero sequence number.

Otherwise Windows guests would not be able to get a correct clocksource
(QueryPerformanceCounter will always return 0) which causes serious chaos.

Signed-off-by: Xiaoming Gao <newtongao@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f32a02578c0d..f6449334ec45 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1898,7 +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;
-		if (kvm_write_guest(kvm, data,
+		if (kvm_write_guest(kvm, gfn << HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT,
 			&tsc_ref, sizeof(tsc_ref)))
 			return 1;
 		mark_page_dirty(kvm, gfn);


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