linux-kernel - [PATCH 0/3] vhost_task: KVM: Fix a race where KVM wakes an exited task

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Message-ID: <20250826004012.3835150-1-seanjc@google.com>
Date: Mon, 25 Aug 2025 17:40:08 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>
Cc: kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 0/3] vhost_task: KVM: Fix a race where KVM wakes an exited task

Fix a bug where KVM attempts to wake a vhost task that has already exited in
response to a fatal signal, and tack on a few cleanups to harden against
introducing similar bugs in the future.

Somehow, this only started causing problems when commit 56180dd20c19 ("futex:
Use RCU-based per-CPU reference counting instead of rcuref_t") landed.  I have
no idea why the futex changes exposed the bug, and I don't care all that much,
as this is firmly a KVM bug.

Sean Christopherson (3):
  vhost_task: KVM: Don't wake KVM x86's recovery thread if vhost task
    was killed
  vhost_task: Allow caller to omit handle_sigkill() callback
  KVM: x86/mmu: Don't register a sigkill callback for NX hugepage
    recovery tasks

 arch/x86/kvm/mmu/mmu.c           |  9 ++----
 include/linux/sched/vhost_task.h |  1 +
 kernel/vhost_task.c              | 52 +++++++++++++++++++++++++++++---
 3 files changed, 51 insertions(+), 11 deletions(-)


base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
-- 
2.51.0.261.g7ce5a0a67e-goog