• Haozhong Zhang's avatar
    KVM: x86: Use adjustment in guest cycles when handling MSR_IA32_TSC_ADJUST · 49102e95
    Haozhong Zhang authored
    commit d7add054 upstream.
    
    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: default avatarHaozhong Zhang <haozhong.zhang@intel.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    49102e95
x86.c 202 KB