linux-kernel - Re: [RFC PATCH v12 07/33] KVM: Add KVM_EXIT_MEMORY

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Message-ID: <ZQ3CaxXY1uUETsI5@google.com>
Date:   Fri, 22 Sep 2023 09:35:55 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Xiaoyao Li <xiaoyao.li@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>, kvm@...r.kernel.org,
        kvmarm@...ts.linux.dev, kvm-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>
Subject: Re: [RFC PATCH v12 07/33] KVM: Add KVM_EXIT_MEMORY_FAULT exit to
 report faults to userspace

On Fri, Sep 22, 2023, Sean Christopherson wrote:
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 7c0e38752526..d13b646188e5 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4184,6 +4184,16 @@ static long kvm_vcpu_ioctl(struct file *filp,
>  				synchronize_rcu();
>  			put_pid(oldpid);
>  		}
> +
> +		/*
> +		 * Reset the exit reason if the previous userspace exit was due
> +		 * to a memory fault.  Not all -EFAULT exits are annotated, and
> +		 * so leaving exit_reason set to KVM_EXIT_MEMORY_FAULT could
> +		 * result in feeding userspace stale information.
> +		 */
> +		if (vcpu->run->exit_reason == KVM_EXIT_MEMORY_FAULT)
> +			vcpu->run->exit_reason = KVM_EXIT_UNKNOWN

Darn semicolons.  Doesn't look like I botched anything else though.

> +
>  		r = kvm_arch_vcpu_ioctl_run(vcpu);
>  		trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
>  		break;
> 
> base-commit: 2358793cd9062b068ac25ac9c965c00d685eea92
> -- 
> 2.42.0.515.g380fc7ccd1-goog
>