From nobody Sat Feb 7 18:28:57 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 65F3C33F39E for ; Fri, 23 Jan 2026 02:28:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769135323; cv=none; b=gmbnRauhIuI24s4jQQIczId3zxS+q3UtuvwhVDBtEF4JAme3m9R9v6wt7h1KF9Zl3bFiLb8MMssvd4C2pil3jiCvcoOUCI3Gmj4S7loSjnybd3pBId81/IB/int/H7PY/eGfZmSabx0HRFS2qXtyYoc5nA1k8TlazXfUwO5LTy0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769135323; c=relaxed/simple; bh=63dVKbKO3JaI73AE0k6OHvOIn2rPwCEpzEbehvxWxV0=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=s3lOYwl3DQnMDiLJjwT3VA9cH9KuZaDB0syuXBGUXLbDnQHyGkohNLR+JkaqlbIECR5bWIEUpDwpVIIkqgN5isL666RMghE0CmE9iNqtzNJqecmd2F5VWa49vPSGUlgWlMhr8IhSdKVU1F5dW9Fc7enWu996fygSchB50K8bQQQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=C9mbwyFG; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="C9mbwyFG" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c5269fcecdeso819993a12.0 for ; Thu, 22 Jan 2026 18:28:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1769135299; x=1769740099; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=juptXMUWjnhIP87dblh4tSUOsWlzJL1NA0+WSTXGUFA=; b=C9mbwyFGgQvBAj3T/tLddPrt6uatxQtSjW9aL0o1qa3p6cwIRpkBm2evFXTtumCLtI 0XvwnsXYDryEhWcslohva08aQyjeP89a7LnVQwPgPR2YWcHEPMSwD6M3b0e/TyMHe0Jt ZtOXKvxR9OQ/pNK4nVYy++9r/gdldSUj/ccw31LsOkVyJozFX+qH9f2PZtKRQrFojrE0 nLfeBRkT7sa/RXC2HcH4T4eCX/37uqjwI2my6N1leriTwDyRDnt8qo78JIT5AnEHoL7F /n45G3uzutEDjLFdCLAcDrnXiOTFQo7os/11m/32iU/G8RcArr4ICeHlR0/99oMGfLM8 tHXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769135299; x=1769740099; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=juptXMUWjnhIP87dblh4tSUOsWlzJL1NA0+WSTXGUFA=; b=K7VbkqDJS4dh1IXmlAsPbb9YAlAEFA0n/ijW4+xRvXkVNX4Q9i4RmgSyJCtk8cXqPm GY9f5b/7KqiFiIhfBRip74/O+pod8zRwvorALOv3Njgm4Q18tBTCyBly6cBvhshsf9en NL6RsBgRsq2KAt4hpzNyLNDThCFPfLtWNtVPxsh4+uRCzNTxq1Wujtun8c1IJVGkyQld 9lDE5dlbJ68PmVuqXPesTAh4SvjqnmBloYd2hYwsbdSYBtnZGtLKuVF3D8EIpiLfw621 WlFDgMHEt6pPHhc0QgXqcQM+6sPC6/tw+U08lZY9X76y0n59ATnabvd/wX4jP2Sdidmr yJig== X-Forwarded-Encrypted: i=1; AJvYcCVl1NTpLbw9p6EptbC2qKTLr1iz9bfXQXYb7/t/EeKTfnkgOdIRBJjByWm0ey+ctTuSIDyTV2q+EohtHwM=@vger.kernel.org X-Gm-Message-State: AOJu0Yx/UfuepPsvOvTukJYiTolaMYJjfHLgUBg56BGhP5jLNFzXC8Eq qBCOrKkCdqdE1dXd72ylmFkhYNXvBUrOyRcfUa/NCC2X8HiQc31232dT8AW+LBZPROWqNIGsgem 31M/4ig== X-Received: from pgbeu11.prod.google.com ([2002:a05:6a02:478b:b0:c63:5307:a545]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:682:b0:371:7f31:17f with SMTP id adf61e73a8af0-38e6f863483mr1494983637.77.1769135298664; Thu, 22 Jan 2026 18:28:18 -0800 (PST) Reply-To: Sean Christopherson Date: Thu, 22 Jan 2026 18:28:16 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260123022816.2283567-1-seanjc@google.com> Subject: [PATCH] KVM: x86: Drop WARN on INIT/SIPI being blocked when vCPU is in Wait-For-SIPI From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+59f2c3a3fc4f6c09b8cd@syzkaller.appspotmail.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Simply drop the WARN as it hasn't detected any meaningful KVM bugs in years (if ever?), and preventing userspace from clobbering guest state is generally a non-goal. More importantly, fully closing the hole would likely require enforcing some amount of ordering in KVM's ioctls, which is a much bigger risk than simply deleting the WARN. Reported-by: syzbot+59f2c3a3fc4f6c09b8cd@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6925da1b.a70a0220.d98e3.00b0.GAE@google= .com Signed-off-by: Sean Christopherson --- arch/x86/kvm/lapic.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 2e513f1c8988..46ba9df3b81d 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -3487,7 +3487,6 @@ int kvm_apic_accept_events(struct kvm_vcpu *vcpu) * wait-for-SIPI (WFS). */ if (!kvm_apic_init_sipi_allowed(vcpu)) { - WARN_ON_ONCE(vcpu->arch.mp_state =3D=3D KVM_MP_STATE_INIT_RECEIVED); clear_bit(KVM_APIC_SIPI, &apic->pending_events); return 0; } base-commit: acdc5446135932ca974b82d9d9a17762c7a82493 --=20 2.52.0.457.g6b5491de43-goog