From: Zelin Deng zelin.deng@linux.alibaba.com
commit d9130a2dfdd4b21736c91b818f87dbc0ccd1e757 upstream.
When MSR_IA32_TSC_ADJUST is written by guest due to TSC ADJUST feature especially there's a big tsc warp (like a new vCPU is hot-added into VM which has been up for a long time), tsc_offset is added by a large value then go back to guest. This causes system time jump as tsc_timestamp is not adjusted in the meantime and pvclock monotonic character. To fix this, just notify kvm to update vCPU's guest time before back to guest.
Cc: stable@vger.kernel.org Signed-off-by: Zelin Deng zelin.deng@linux.alibaba.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Message-Id: 1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/x86.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2172,6 +2172,10 @@ int kvm_set_msr_common(struct kvm_vcpu * if (!msr_info->host_initiated) { s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr; adjust_tsc_offset_guest(vcpu, adj); + /* Before back to guest, tsc_timestamp must be adjusted + * as well, otherwise guest's percpu pvclock time could jump. + */ + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); } vcpu->arch.ia32_tsc_adjust_msr = data; }