linux-kernel - Re: [PATCH v19 078/130] KVM: TDX: Implement TDX vcpu enter/exit path

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Message-ID: <7a24c01a03f68a87b0bbfa82a5d6ccbf3cbd6f4b.camel@intel.com>
Date: Mon, 18 Mar 2024 21:01:05 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Yamahata,
 Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>, "Huang, Kai"
	<kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>
Subject: Re: [PATCH v19 078/130] KVM: TDX: Implement TDX vcpu enter/exit path

On Mon, 2024-02-26 at 00:26 -0800, isaku.yamahata@...el.com wrote:
> +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
> +{
> +       struct vcpu_tdx *tdx = to_tdx(vcpu);
> +
> +       if (unlikely(!tdx->initialized))
> +               return -EINVAL;
> +       if (unlikely(vcpu->kvm->vm_bugged)) {
> +               tdx->exit_reason.full = TDX_NON_RECOVERABLE_VCPU;
> +               return EXIT_FASTPATH_NONE;
> +       }
> +

Isaku, can you elaborate on why this needs special handling? There is a
check in vcpu_enter_guest() like:
	if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) {
		r = -EIO;
		goto out;
	}

Instead it returns a SEAM error code for something actuated by KVM. But
can it even be reached because of the other check? Not sure if there is
a problem, just sticks out to me and wondering whats going on.