linux-kernel - Re: [PATCH] KVM: x86: Drop WARN on INIT/SIPI being blocked when vCPU is in Wait-For-SIPI

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Message-ID: <177016367951.574529.16511584559819900521.b4-ty@google.com>
Date: Tue,  3 Feb 2026 16:10:13 -0800
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, 
	syzbot+59f2c3a3fc4f6c09b8cd@...kaller.appspotmail.com
Subject: Re: [PATCH] KVM: x86: Drop WARN on INIT/SIPI being blocked when vCPU
 is in Wait-For-SIPI

On Thu, 22 Jan 2026 18:28:16 -0800, Sean Christopherson wrote:
> Drop the sanity check in kvm_apic_accept_events() that attempts to detect
> KVM bugs by asserting that a vCPU isn't in Wait-For-SIPI if INIT/SIPI are
> blocked, because if INIT is blocked, then it should be impossible for a
> vCPU to get into WFS in the first place.  Unfortunately, syzbot is smarter
> than KVM (and its maintainers), and circumvented the guards put in place
> by commit 0fe3e8d804fd ("KVM: x86: Move INIT_RECEIVED vs. INIT/SIPI blocked
> check to KVM_RUN") by swapping the order and stuffing VMXON after INIT, and
> then triggering kvm_apic_accept_events() by way of KVM_GET_MP_STATE.
> 
> [...]

Applied to kvm-x86 misc.

[1/1] KVM: x86: Drop WARN on INIT/SIPI being blocked when vCPU is in Wait-For-SIPI
      https://github.com/kvm-x86/linux/commit/c4a365cd4a4e

--
https://github.com/kvm-x86/linux/tree/next