linux-kernel - Re: [PATCH] KVM: nVMX: fixes for preemption timer migration

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Date:   Thu, 9 Jul 2020 10:23:22 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>, Bandan Das <bsd@...hat.com>,
        Makarand Sonare <makarandsonare@...gle.com>
Subject: Re: [PATCH] KVM: nVMX: fixes for preemption timer migration

On Thu, Jul 9, 2020 at 10:15 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> Commit 850448f35aaf ("KVM: nVMX: Fix VMX preemption timer migration",
> 2020-06-01) accidentally broke nVMX live migration from older version
> by changing the userspace ABI.  Restore it and, while at it, ensure
> that vmx->nested.has_preemption_timer_deadline is always initialized
> according to the KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE flag.
>
> Cc: Makarand Sonare <makarandsonare@...gle.com>
> Fixes: 850448f35aaf ("KVM: nVMX: Fix VMX preemption timer migration")
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/include/uapi/asm/kvm.h | 5 +++--
>  arch/x86/kvm/vmx/nested.c       | 3 ++-
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 17c5a038f42d..0780f97c1850 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -408,14 +408,15 @@ struct kvm_vmx_nested_state_data {
>  };
>
>  struct kvm_vmx_nested_state_hdr {
> -       __u32 flags;
>         __u64 vmxon_pa;
>         __u64 vmcs12_pa;
> -       __u64 preemption_timer_deadline;
>
>         struct {
>                 __u16 flags;
>         } smm;
> +
> +       __u32 flags;
> +       __u64 preemption_timer_deadline;
>  };
>
>  struct kvm_svm_nested_state_data {
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index b26655104d4a..3fc2411edc92 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -6180,7 +6180,8 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
>                 vmx->nested.has_preemption_timer_deadline = true;
>                 vmx->nested.preemption_timer_deadline =
>                         kvm_state->hdr.vmx.preemption_timer_deadline;
> -       }
> +       } else
> +               vmx->nested.has_preemption_timer_deadline = false;

Doesn't the coding standard require braces around the else clause?

Reviewed-by: Jim Mattson <jmattson@...gle.com>