linux-kernel - Re: [PATCH 7/7] KVM: VMX: Handle NMI VM-Exits in noinstr region

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Date:   Thu, 19 Jan 2023 15:39:55 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 7/7] KVM: VMX: Handle NMI VM-Exits in noinstr region

On Thu, Jan 19, 2023, Peter Zijlstra wrote:
> On Tue, Dec 13, 2022 at 06:09:12AM +0000, Sean Christopherson wrote:
> 
> > @@ -7119,6 +7118,18 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
> >  
> >  	vmx_enable_fb_clear(vmx);
> >  
> > +	if (unlikely(vmx->fail))
> > +		vmx->exit_reason.full = 0xdead;
> > +	else
> > +		vmx->exit_reason.full = vmcs_read32(VM_EXIT_REASON);
> > +
> > +	if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI &&
> > +	    is_nmi(vmx_get_intr_info(vcpu))) {
> > +		kvm_before_interrupt(vcpu, KVM_HANDLING_NMI);
> > +		vmx_do_nmi_irqoff();
> > +		kvm_after_interrupt(vcpu);
> > +	}
> > +
> >  	guest_state_exit_irqoff();
> >  }
> 
> I think we're going to have to sprinkle __always_inline on the
> kvm_{before,after}_interrupt() things (or I missed the earlier patches
> doing this already), sometimes compilers are just weird.

It's in this patch, just lurking at the bottom.

> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 9de72586f406..44d1827f0a30 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -382,13 +382,13 @@ enum kvm_intr_type {
>         KVM_HANDLING_NMI,
>  };
>
> -static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu,
> -                                       enum kvm_intr_type intr)
> +static __always_inline void kvm_before_interrupt(struct kvm_vcpu *vcpu,
> +                                                enum kvm_intr_type intr)
>  {
>         WRITE_ONCE(vcpu->arch.handling_intr_from_guest, (u8)intr);
>  }
>
> -static inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
> +static __always_inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
>  {
>         WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 0);
>  }