linux-kernel - [RFC PATCH v2 00/18] KVM: x86/mmu: TDX post-populate cleanups

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Message-ID: <20250829000618.351013-1-seanjc@google.com>
Date: Thu, 28 Aug 2025 17:06:00 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Ira Weiny <ira.weiny@...el.com>, Kai Huang <kai.huang@...el.com>, 
	Michael Roth <michael.roth@....com>, Yan Zhao <yan.y.zhao@...el.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [RFC PATCH v2 00/18] KVM: x86/mmu: TDX post-populate cleanups

New (still largely untested) version of the TDX post-populate cleanup series
to address locking issues between gmem and TDX's post-populate hook[*], with
a pile of related cleanups throw in to (hopefully) simplify future development,
e.g. for hugepage and in-place conversion.

RFC as this is compile tested only again, and there are substantial differences
relative to v1.

P.S. I wasn't intending this to be 6.18 material (at all), but with the change
     in how TDH_MEM_PAGE_ADD is handled, I'm tempted to make a push to get this
     in sooner than later so that in-flight development can benefit.  Thoughts?

[*] http://lore.kernel.org/all/aG_pLUlHdYIZ2luh@google.com

v2:
 - Collect a few reviews (and ignore some because the patches went away).
   [Rick, Kai, Ira]
 - Move TDH_MEM_PAGE_ADD under mmu_lock and drop nr_premapped. [Yan, Rick]
 - Force max_level = PG_LEVEL_4K straightaway. [Yan]
 - s/kvm_tdp_prefault_page/kvm_tdp_page_prefault. [Rick]
 - Use Yan's version of "Say no to pinning!".  [Yan, Rick]
 - Tidy up helpers and macros to reduce boilerplate and copy+pate code, and
   to eliminate redundant/dead code (e.g. KVM_BUG_ON() the same error
   multiple times).
 - KVM_BUG_ON() if TDH_MR_EXTEND fails (I convinced myself it can't).

v1: https://lore.kernel.org/all/20250827000522.4022426-1-seanjc@google.com

Sean Christopherson (17):
  KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings
  KVM: x86/mmu: Add dedicated API to map guest_memfd pfn into TDP MMU
  Revert "KVM: x86/tdp_mmu: Add a helper function to walk down the TDP
    MMU"
  KVM: x86/mmu: Rename kvm_tdp_map_page() to kvm_tdp_page_prefault()
  KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG_ON() condition
  KVM: TDX: Fold tdx_sept_drop_private_spte() into
    tdx_sept_remove_private_spte()
  KVM: x86/mmu: Drop the return code from
    kvm_x86_ops.remove_external_spte()
  KVM: TDX: Avoid a double-KVM_BUG_ON() in tdx_sept_zap_private_spte()
  KVM: TDX: Use atomic64_dec_return() instead of a poor equivalent
  KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller
  KVM: TDX: Bug the VM if extended the initial measurement fails
  KVM: TDX: ADD pages to the TD image while populating mirror EPT
    entries
  KVM: TDX: Fold tdx_sept_zap_private_spte() into
    tdx_sept_remove_private_spte()
  KVM: TDX: Combine KVM_BUG_ON + pr_tdx_error() into TDX_BUG_ON()
  KVM: TDX: Derive error argument names from the local variable names
  KVM: TDX: Assert that mmu_lock is held for write when removing S-EPT
    entries
  KVM: TDX: Add macro to retry SEAMCALLs when forcing vCPUs out of guest

Yan Zhao (1):
  KVM: TDX: Drop superfluous page pinning in S-EPT management

 arch/x86/include/asm/kvm_host.h |   4 +-
 arch/x86/kvm/mmu.h              |   3 +-
 arch/x86/kvm/mmu/mmu.c          |  66 ++++-
 arch/x86/kvm/mmu/tdp_mmu.c      |  45 +---
 arch/x86/kvm/vmx/tdx.c          | 460 +++++++++++---------------------
 arch/x86/kvm/vmx/tdx.h          |   8 +-
 6 files changed, 234 insertions(+), 352 deletions(-)


base-commit: ecbcc2461839e848970468b44db32282e5059925
-- 
2.51.0.318.gd7df087d1a-goog