From 76df7b6d4dcfd9cccdc4838713e5b94f1233aedf Mon Sep 17 00:00:00 2001 From: Zelin Deng Date: Wed, 28 Apr 2021 10:22:01 +0800 Subject: [PATCH] KVM: x86: Update vCPU's hv_clock before back to guest when tsc_offset is adjusted 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 Signed-off-by: Paolo Bonzini Message-Id: <1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1a00af1b076b6..28ef141557264 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3321,6 +3321,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 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; } -- 2.39.5