KVM: x86: Use adjustment in guest cycles when handling MSR_IA32_TSC_ADJUST

When kvm_set_msr_common() handles a guest's write to
MSR_IA32_TSC_ADJUST, it will calcuate an adjustment based on the data
written by guest and then use it to adjust TSC offset by calling a
call-back adjust_tsc_offset(). The 3rd parameter of adjust_tsc_offset()
indicates whether the adjustment is in host TSC cycles or in guest TSC
cycles. If SVM TSC scaling is enabled, adjust_tsc_offset()
[i.e. svm_adjust_tsc_offset()] will first scale the adjustment;
otherwise, it will just use the unscaled one. As the MSR write here
comes from the guest, the adjustment is in guest TSC cycles. However,
the current kvm_set_msr_common() uses it as a value in host TSC
cycles (by using true as the 3rd parameter of adjust_tsc_offset()),
which can result in an incorrect adjustment of TSC offset if SVM TSC
scaling is enabled. This patch fixes this problem.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Cc: stable@vger.linux.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c5e88a88189958220bfdede6841692b8fd146be7..8f0f6eca69da1dc6db95c16782871580bf57091d 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2105,7 +2105,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                if (guest_cpuid_has_tsc_adjust(vcpu)) {
                        if (!msr_info->host_initiated) {
                                s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr;
-                               kvm_x86_ops->adjust_tsc_offset(vcpu, adj, true);
+                               adjust_tsc_offset_guest(vcpu, adj);
                        }
                        vcpu->arch.ia32_tsc_adjust_msr = data;
                }