linux-kernel - Re: [PATCH v2 1/9] KVM: x86: check validity of argument to KVM_SET_MP

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Message-ID: <26f6e26110b99e0a8cace173a221694d4e94cc1c.camel@redhat.com>
Date:   Mon, 15 Aug 2022 16:31:58 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, vkuznets@...hat.com
Subject: Re: [PATCH v2 1/9] KVM: x86: check validity of argument to
 KVM_SET_MP_STATE

On Thu, 2022-08-11 at 17:05 -0400, Paolo Bonzini wrote:
> An invalid argument to KVM_SET_MP_STATE has no effect other than making the
> vCPU fail to run at the next KVM_RUN.  Since it is extremely unlikely that
> any userspace is relying on it, fail with -EINVAL just like for other
> architectures.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 132d662d9713..c44348bb6ef2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10653,7 +10653,8 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
>         case KVM_MP_STATE_INIT_RECEIVED:
>                 break;
>         default:
> -               return -EINTR;
> +               WARN_ON(1);

Very small nitpick: Maybe WARN_ON_ONCE after all? 
(but I don't see any way after this patch to have invalid mp_state)

> +               break;



>         }
>         return 1;
>  }
> @@ -11094,9 +11095,22 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
>  
>         vcpu_load(vcpu);
>  
> -       if (!lapic_in_kernel(vcpu) &&
> -           mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
> +       switch (mp_state->mp_state) {
> +       case KVM_MP_STATE_UNINITIALIZED:
> +       case KVM_MP_STATE_HALTED:
> +       case KVM_MP_STATE_AP_RESET_HOLD:
> +       case KVM_MP_STATE_INIT_RECEIVED:
> +       case KVM_MP_STATE_SIPI_RECEIVED:
> +               if (!lapic_in_kernel(vcpu))
> +                       goto out;
> +               break;
> +
> +       case KVM_MP_STATE_RUNNABLE:
> +               break;
> +
> +       default:
>                 goto out;
> +       }
>  
>         /*
>          * KVM_MP_STATE_INIT_RECEIVED means the processor is in



Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky