linux-kernel - [GIT PULL] KVM: guest

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Message-ID: <20260207041011.913471-4-seanjc@google.com>
Date: Fri,  6 Feb 2026 20:10:05 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sean Christopherson <seanjc@...gle.com>
Subject: [GIT PULL] KVM: guest_memfd changes for 6.20

In preparation (pun intended) for in-place conversion, drop gmem's preparation
tracking, GUP source pages outside of filemap invalidate lock to avoid AB-BA
locking, and require source pages to be 4KiB aligned.

Regarding the retroactive alignment requirement, I know we discussed it in PUCK,
but I forget if we ever formalized a decision there.  After going over various
VMMs, we gained enough confidence to just bite the bullet and hope for the best.

The following changes since commit 9ace4753a5202b02191d54e9fdf7f9e3d02b85eb:

  Linux 6.19-rc4 (2026-01-04 14:41:55 -0800)

are available in the Git repository at:

  https://github.com/kvm-x86/linux.git tags/kvm-x86-gmem-6.20

for you to fetch changes up to 2a62345b30529e488beb6a1220577b3495933724:

  KVM: guest_memfd: GUP source pages prior to populating guest memory (2026-01-15 12:31:17 -0800)

----------------------------------------------------------------
KVM guest_memfd changes for 6.20

 - Remove kvm_gmem_populate()'s preparation tracking and half-baked hugepage
   handling, and instead rely on SNP (the only user of the tracking) to do its
   own tracking via the RMP.

 - Retroactively document and enforce (for SNP) that KVM_SEV_SNP_LAUNCH_UPDATE
   and KVM_TDX_INIT_MEM_REGION require the source page to be 4KiB aligned, to
   avoid non-trivial complexity for a non-existent usecase (and because
   in-place conversion simply can't support unaligned sources).

 - When populating guest_memfd memory, GUP the source page in common code and
   pass the refcounted page to the vendor callback, instead of letting vendor
   code do the heavy lifting.  Doing so avoids a looming deadlock bug with
   in-place due an AB-BA conflict betwee mmap_lock and guest_memfd's filemap
   invalidate lock.

----------------------------------------------------------------
Michael Roth (5):
      KVM: guest_memfd: Remove partial hugepage handling from kvm_gmem_populate()
      KVM: guest_memfd: Remove preparation tracking
      KVM: SEV: Document/enforce page-alignment for KVM_SEV_SNP_LAUNCH_UPDATE
      KVM: TDX: Document alignment requirements for KVM_TDX_INIT_MEM_REGION
      KVM: guest_memfd: GUP source pages prior to populating guest memory

Yan Zhao (1):
      KVM: SVM: Fix a missing kunmap_local() in sev_gmem_post_populate()

 .../virt/kvm/x86/amd-memory-encryption.rst         |   2 +-
 Documentation/virt/kvm/x86/intel-tdx.rst           |   2 +-
 arch/x86/kvm/svm/sev.c                             | 108 +++++++---------
 arch/x86/kvm/vmx/tdx.c                             |  16 +--
 include/linux/kvm_host.h                           |   4 +-
 virt/kvm/guest_memfd.c                             | 139 +++++++++++----------
 6 files changed, 130 insertions(+), 141 deletions(-)