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Re: [PATCH] i386: Fix KVM_CAP_ADJUST_CLOCK capability check
From: |
Marcelo Tosatti |
Subject: |
Re: [PATCH] i386: Fix KVM_CAP_ADJUST_CLOCK capability check |
Date: |
Tue, 20 Sep 2022 15:33:55 -0300 |
On Tue, Sep 20, 2022 at 04:40:24PM +0200, Vitaly Kuznetsov wrote:
> KVM commit c68dc1b577ea ("KVM: x86: Report host tsc and realtime values in
> KVM_GET_CLOCK") broke migration of certain workloads, e.g. Win11 + WSL2
> guest reboots immediately after migration. KVM, however, is not to
> blame this time. When KVM_CAP_ADJUST_CLOCK capability is checked, the
> result is all supported flags (which the above mentioned KVM commit
> enhanced) but kvm_has_adjust_clock_stable() wants it to be
> KVM_CLOCK_TSC_STABLE precisely. The result is that 'clock_is_reliable'
> is not set in vmstate and the saved clock reading is discarded in
> kvmclock_vm_state_change().
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> target/i386/kvm/kvm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index a1fd1f53791d..c33192a87dcb 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -157,7 +157,7 @@ bool kvm_has_adjust_clock_stable(void)
> {
> int ret = kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK);
>
> - return (ret == KVM_CLOCK_TSC_STABLE);
> + return ret & KVM_CLOCK_TSC_STABLE;
> }
>
> bool kvm_has_adjust_clock(void)
> --
> 2.37.3
>
>
ACK.