linux-kernel - Re: [RFC PATCH v5 064/104] KVM: TDX: Implement TDX vcpu enter/exit path

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Date:   Wed, 23 Mar 2022 10:55:52 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Erdem Aktas <erdemaktas@...gle.com>
Cc:     "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "open list:KERNEL VIRTUAL MACHINE (KVM)" <kvm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 064/104] KVM: TDX: Implement TDX vcpu enter/exit
 path

On Tue, Mar 22, 2022 at 10:28:42AM -0700,
Erdem Aktas <erdemaktas@...gle.com> wrote:

> On Fri, Mar 4, 2022 at 11:50 AM <isaku.yamahata@...el.com> wrote:
> > @@ -509,6 +512,37 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> >         vcpu->kvm->vm_bugged = true;
> >  }
> >
> > +u64 __tdx_vcpu_run(hpa_t tdvpr, void *regs, u32 regs_mask);
> > +
> > +static noinstr void tdx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
> > +                                       struct vcpu_tdx *tdx)
> > +{
> > +       guest_enter_irqoff();
> > +       tdx->exit_reason.full = __tdx_vcpu_run(tdx->tdvpr.pa, vcpu->arch.regs, 0);
> > +       guest_exit_irqoff();
> > +}
> > +
> > +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
> > +{
> > +       struct vcpu_tdx *tdx = to_tdx(vcpu);
> > +
> > +       if (unlikely(vcpu->kvm->vm_bugged)) {
> > +               tdx->exit_reason.full = TDX_NON_RECOVERABLE_VCPU;
> > +               return EXIT_FASTPATH_NONE;
> > +       }
> > +
> > +       trace_kvm_entry(vcpu);
> > +
> > +       tdx_vcpu_enter_exit(vcpu, tdx);
> > +
> > +       vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
> > +       trace_kvm_exit(vcpu, KVM_ISA_VMX);
> > +
> > +       if (tdx->exit_reason.error || tdx->exit_reason.non_recoverable)
> > +               return EXIT_FASTPATH_NONE;
> 
> Looks like the above if statement has no effect. Just checking if this
> is intentional.

I'm not sure if I get your point.  tdx->exit_reason is updated by the above
tdx_cpu_enter_exit().  So it makes sense to check .error or .non_recoverable.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>