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Commit 1735cec1 authored by Zelin Deng's avatar Zelin Deng Committed by Greg Kroah-Hartman
Browse files

KVM: x86: Update vCPU's hv_clock before back to guest when tsc_offset is adjusted 



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: default avatarZelin Deng <zelin.deng@linux.alibaba.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <1619576521-81399-2-git-send-email-zelin.deng@linux.alibaba.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 20fff3ef

arch/x86/kvm/x86.c

+4 −0
Original line number Diff line number Diff line
@@ -2764,6 +2764,10 @@ 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;

		}