linux-kernel - [PATCH 3.14 68/94] kvm: fix wrong address when writing Hyper-V tsc page

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Date:	Mon,  7 Jul 2014 16:57:58 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Xiaoming Gao <newtongao@...cnet.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 3.14 68/94] kvm: fix wrong address when writing Hyper-V tsc page

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xiaoming Gao <newtongao@...cent.com>

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@...cnet.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/x86.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1866,7 +1866,7 @@ static int set_msr_hyperv_pw(struct kvm_
 		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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