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

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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: [email protected]
Signed-off-by: Zelin Deng <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
This commit is contained in:
Zelin Deng
2021-09-06 07:07:03 -04:00
committed by Paolo Bonzini
parent 4ac214574d
commit d9130a2dfd
1 changed files with 4 additions and 0 deletions
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arch/x86/kvm/x86.c
+4
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@@ -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;
}