linux-kernel - Re: [GIT PULL] KVM: x86: MMU changes for 6.18

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Message-ID: <CABgObfaJ7ZBVhY5Fcmh9rfa6w8ji8v33JShUjb5-uZQVZRWHzg@mail.gmail.com>
Date: Tue, 30 Sep 2025 19:33:48 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: x86: MMU changes for 6.18

On Sat, Sep 27, 2025 at 8:09 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Recover TDP MMU NX huge pages under read lock, and fix two (interruptible)
> deadlocks in prefaulting and in the TDX anti-zero-step code (there's a
> selftest from Yan for the prefaulting case that I'll send along later).
>
> The following changes since commit c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9:
>
>   Linux 6.17-rc2 (2025-08-17 15:22:10 -0700)
>
> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-mmu-6.18
>
> for you to fetch changes up to 2bc2694fe20bf06eb73524426e3f4581d7b28923:
>
>   KVM: TDX: Do not retry locally when the retry is caused by invalid memslot (2025-09-10 12:06:35 -0700)

Pulled, thanks.

> ----------------------------------------------------------------
> KVM x86 MMU changes for 6.18
>
>  - Recover possible NX huge pages within the TDP MMU under read lock to
>    reduce guest jitter when restoring NX huge pages.
>
>  - Return -EAGAIN during prefault if userspace concurrently deletes/moves the
>    relevant memslot to fix an issue where prefaulting could deadlock with the
>    memslot update.
>
>  - Don't retry in TDX's anti-zero-step mitigation if the target memslot is
>    invalid, i.e. is being deleted or moved, to fix a deadlock scenario similar
>    to the aforementioned prefaulting case.
>
> ----------------------------------------------------------------
> Sean Christopherson (2):
>       KVM: x86/mmu: Return -EAGAIN if userspace deletes/moves memslot during prefault
>       KVM: TDX: Do not retry locally when the retry is caused by invalid memslot
>
> Vipin Sharma (3):
>       KVM: x86/mmu: Track possible NX huge pages separately for TDP vs. Shadow MMU
>       KVM: x86/mmu: Rename kvm_tdp_mmu_zap_sp() to better indicate its purpose
>       KVM: x86/mmu: Recover TDP MMU NX huge pages using MMU read lock
>
>  arch/x86/include/asm/kvm_host.h |  39 ++++++----
>  arch/x86/kvm/mmu/mmu.c          | 165 ++++++++++++++++++++++++++--------------
>  arch/x86/kvm/mmu/mmu_internal.h |   6 +-
>  arch/x86/kvm/mmu/tdp_mmu.c      |  49 +++++++++---
>  arch/x86/kvm/mmu/tdp_mmu.h      |   3 +-
>  arch/x86/kvm/vmx/tdx.c          |  11 +++
>  virt/kvm/kvm_main.c             |   1 +
>  7 files changed, 192 insertions(+), 82 deletions(-)
>