Re: [GIT PULL] KVM: x86: MMU changes for 7.1

[Paolo Bonzini]

On Sat, Apr 11, 2026 at 1:58 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Fix an amusing UBSAN warning where nx_huge_pages can be read before KVM is
> fully loaded, optimize the unsync flow, and micro-optimize hugepage splitting
> in the TDP MMU.
>
> The following changes since commit 11439c4635edd669ae435eec308f4ab8a0804808:
>
>   Linux 7.0-rc2 (2026-03-01 15:39:31 -0800)
>
> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-mmu-7.1
>
> for you to fetch changes up to b3ae3ceb556945724d0c046ddb4ea0cf492a0ce6:
>
>   KVM: x86/mmu: KVM: x86/mmu: Skip unsync when large pages are allowed (2026-03-12 10:36:01 -0700)
>
> ----------------------------------------------------------------
> KVM x86 MMU changes for 7.1
>
>  - Fix an undefined behavior warning where a crafty userspace can read kvm.ko's
>    nx_huge_pages before it's fully initialized.
>
>  - Don't zero-allocate page tables that are used for splitting hugepages in the
>    TDP MMU, as KVM is guaranteed to set all SPTEs in the page table and thus
>    write all bytes.
>
>  - Bail early when trying to unsync 4KiB mappings if the target gfn can be
>    mapped with a 2MiB hugepage, to avoid the gfn hash lookup.
>
> ----------------------------------------------------------------

Pulled, thanks.

> Gal Pressman (1):
>       KVM: x86/mmu: Fix UBSAN warning when reading nx_huge_pages parameter
>
> Lai Jiangshan (1):
>       KVM: x86/mmu: KVM: x86/mmu: Skip unsync when large pages are allowed
>
> Sean Christopherson (1):
>       KVM: x86/mmu: Don't zero-allocate page table used for splitting a hugepage
>
>  arch/x86/kvm/mmu/mmu.c     | 14 ++++++++++++++
>  arch/x86/kvm/mmu/tdp_mmu.c |  2 +-
>  2 files changed, 15 insertions(+), 1 deletion(-)
>