linux-kernel - Re: [RFC PATCH 02/12] KVM: x86/mmu: Add dedicated API to map guest

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Message-ID: <aK/9YF6UTHUiOFR6@yzhao56-desk.sh.intel.com>
Date: Thu, 28 Aug 2025 14:55:28 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
CC: "seanjc@...gle.com" <seanjc@...gle.com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"Annapurve, Vishal" <vannapurve@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "michael.roth@....com"
	<michael.roth@....com>, "Weiny, Ira" <ira.weiny@...el.com>
Subject: Re: [RFC PATCH 02/12] KVM: x86/mmu: Add dedicated API to map
 guest_memfd pfn into TDP MMU

On Thu, Aug 28, 2025 at 08:54:48AM +0800, Edgecombe, Rick P wrote:
> On Wed, 2025-08-27 at 16:25 +0800, Yan Zhao wrote:
> > > +{
> > > +	struct kvm_page_fault fault = {
> > > +		.addr = gfn_to_gpa(gfn),
> > > +		.error_code = PFERR_GUEST_FINAL_MASK |
> > > PFERR_PRIVATE_ACCESS,
> > > +		.prefetch = true,
> > > +		.is_tdp = true,
> > > +		.nx_huge_page_workaround_enabled =
> > > is_nx_huge_page_enabled(vcpu->kvm),
> > > +
> > > +		.max_level = KVM_MAX_HUGEPAGE_LEVEL,
> > Looks the kvm_tdp_mmu_map_private_pfn() is only for initial memory mapping,
> > given that ".prefetch = true" and RET_PF_SPURIOUS is not a valid return value.
> 
> Hmm, what are you referring to regarding RET_PF_SPURIOUS?
If kvm_tdp_mmu_map_private_pfn() can also be invoked after initial memory
mapping stage, RET_PF_SPURIOUS is a valid return case.

But in this patch, only RET_PF_RETRY and RET_PF_FIXED are valid.
So, I think it's expected to be invoked only by initial memory mapping stage :)