linux-kernel - Re: [PATCH v2 05/10] KVM: x86/mmu: Introduce kvm_tdp_map

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Date: Tue, 16 Apr 2024 14:46:17 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>
CC: "seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai"
	<kai.huang@...el.com>, "federico.parola@...ito.it"
	<federico.parola@...ito.it>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>, "dmatlack@...gle.com" <dmatlack@...gle.com>,
	"michael.roth@....com" <michael.roth@....com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>
Subject: Re: [PATCH v2 05/10] KVM: x86/mmu: Introduce kvm_tdp_map_page() to
 populate guest memory

On Wed, 2024-04-10 at 15:07 -0700, isaku.yamahata@...el.com wrote:
>  
> +int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
> +                    u8 *level)
> +{
> +       int r;
> +
> +       /* Restrict to TDP page fault. */
> +       if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault)
> +               return -EINVAL;
> +
> +       r = __kvm_mmu_do_page_fault(vcpu, gpa, error_code, false, NULL,
> level);

Why not prefetch = true? Doesn't it fit? It looks like the behavior will be to
not set the access bit.

> +       if (r < 0)
> +               return r;
> +
> +       switch (r) {
> +       case RET_PF_RETRY:
> +               return -EAGAIN;
> +
> +       case RET_PF_FIXED:
> +       case RET_PF_SPURIOUS:
> +               return 0;
> +
> +       case RET_PF_EMULATE:
> +               return -EINVAL;
> +
> +       case RET_PF_CONTINUE:
> +       case RET_PF_INVALID:
> +       default:
> +               WARN_ON_ONCE(r);
> +               return -EIO;
> +       }
> +}