linux-kernel - Re: [PATCH v3 04/25] KVM: x86/mmu: Add dedicated API to map guest

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Message-ID: <d53248824d03e7dc1dd6facb67a0aab272704875.camel@intel.com>
Date: Tue, 21 Oct 2025 00:10:14 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v3 04/25] KVM: x86/mmu: Add dedicated API to map
 guest_memfd pfn into TDP MMU

On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote:
> Add and use a new API for mapping a private pfn from guest_memfd into the
> TDP MMU from TDX's post-populate hook instead of partially open-coding the
> functionality into the TDX code.  Sharing code with the pre-fault path
> sounded good on paper, but it's fatally flawed as simulating a fault loses
> the pfn, and calling back into gmem to re-retrieve the pfn creates locking
> problems, e.g. kvm_gmem_populate() already holds the gmem invalidation
> lock.
> 
> Providing a dedicated API will also removing several MMU exports that
> ideally would not be exposed outside of the MMU, let alone to vendor code.
> On that topic, opportunistically drop the kvm_mmu_load() export.  Leave
> kvm_tdp_mmu_gpa_is_mapped() alone for now; the entire commit that added
> kvm_tdp_mmu_gpa_is_mapped() will be removed in the near future.
> 
> Cc: Michael Roth <michael.roth@....com>
> Cc: Yan Zhao <yan.y.zhao@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Vishal Annapurve <vannapurve@...gle.com>
> Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Link: https://lore.kernel.org/all/20250709232103.zwmufocd3l7sqk7y@amd.com
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>