From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8B2C480DFC for ; Wed, 1 Jul 2026 15:06:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.180.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782918417; cv=none; b=immDgGxTyoivXA8MRFm8GQJbyIDRlieo8JrwMSulVLG1p6OJo5Lr1i14KCc0ZbFdmgubeK6BT2MMb++GEXQJ/ueLeJ4XxxZn1WD/KTJ2MRiXLVqA6p6s++rc7J+ImvSp2KTZHn2o3gnHZ/7Cze15b6rKqHXdxll8LnyiPqS/70U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782918417; c=relaxed/simple; bh=J2I/xde4R+mq9rPsOBP7hmzn/ps8KRIsDzt31M00GYk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=azrNxblH5ZXzoqVpYV6LDdKP9TyK/EF1mDSvBmoSNWaLPq6iI+7mzD5nWZ5pkotw1/4NgqBNOxUShO0v6fsT6eTOlMPpgpCxHRE2XQTJ/h32zbAb13+3p2mhFEZJuFqDj++aAXYFdk7O8uIss4YtHYsWT8db+BbCMkYhsakNfvU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com; spf=pass smtp.mailfrom=oss.qualcomm.com; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b=pxgQP3aN; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b=OE2ZSwjD; arc=none smtp.client-ip=205.220.180.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b="pxgQP3aN"; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b="OE2ZSwjD" Received: from pps.filterd (m0279871.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 661A8xkZ753602 for ; Wed, 1 Jul 2026 15:06:50 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= 5wuRF73jWKw01AnLgPbUYJZTlfclOfzRgiDuT91g36s=; b=pxgQP3aNlawahaiu +Or+yg/jCVNOEm5r2VgW/a9tc3vFD3cJx1MlyzkrWXh1enB2tHngiOXP5dYwm9SI 3BQrTz8PO5ZVrS4+mK8GjDprZrCwrYwJ1GNZQUqFVo6iNNKjakEDPP7t/sifDMup 8P27j7ClpDs0/efgRFTL5yOMikdf1/NIT3vVeKl4A+AsGY1Qfi5cZP1DYObkZJWs TFWDrwQ86NIJ6dZkNsBygCTO9Rbs0O1dfp+dvSWSTfc8eqjjELiS7iZtIS2x6ryy 2eqOYpZGZt1fLQyhrKXEAarB145s/mHGZrgi2IXR6PigS/rKT7lzYoWdbEJQawHz UpF3DQ== Received: from mail-vk1-f200.google.com (mail-vk1-f200.google.com [209.85.221.200]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4f4rsy3d6w-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Wed, 01 Jul 2026 15:06:50 +0000 (GMT) Received: by mail-vk1-f200.google.com with SMTP id 71dfb90a1353d-5954c5fbcc7so395894e0c.0 for ; Wed, 01 Jul 2026 08:06:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1782918410; x=1783523210; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=5wuRF73jWKw01AnLgPbUYJZTlfclOfzRgiDuT91g36s=; b=OE2ZSwjDfO7zQ4TJwUs6UwWPuetpxVLlN+Dza/NuxVqvB/U+XsIfv0QpiyuGgrVzNX 0CYwth1ArNX87yGnHJr3BGAOQS0UTegh7475dsBk+IPqeIza1w7IYDbRqqOQ81+M9jSI 8ZNvb+RCfBl37yTfWQhhlBNg2o5LVeEaIwrweFKZBeLUOQlxCMTu5ZX8ANQBtx+ykXGc Kw6ZraXcsf+XJBD1woro7c3m4BIROWsXk7OGbtjDmMQ44GtRlMss1ejjppEfd+Q0W0Bt lN7o6KuKa2jd0uBGdSsrM1FVZsrcaIvTUcXIme4pIq9pgjnh1vKAXV9OVenXuv9fGdbL 4RsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782918410; x=1783523210; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=5wuRF73jWKw01AnLgPbUYJZTlfclOfzRgiDuT91g36s=; b=jk6vulWHoFmhlL4SnhZLv4Yu/5r7KYTpq9GnS+F+FWtmFYuBez3alghju1OlhUFe7+ HZIll1rGU+AT550E2JhtWNlG2WGSSHL3B/IeMUuWkDCwthSLvFzMfUxnERH9VxWoSbkw JE44MVy6p4nzIGjxTOVGLqRzmj2R6SW0p8jycumJOG918TVBEjCyRRxo5hbTsTWBEGkc KTAy1Z4irk8PCcwxpsDq2fXP2m2zEfGWrSAKahckXa5Ke72cWmQuqx+NS7cafxT6fzT7 SkObDxNZoc+WQCqasiLefa94pxRBxLQYjBECsK8oOiC2meWRSlDLn/vElqS9l2REBRHZ IZEQ== X-Forwarded-Encrypted: i=1; AHgh+RqDOT/Ufgksa/Nd2lplbLIgb5CxmfPuxknWQWj8g0bADanZukG6C8tceTAKGtDMI/n8kPQTxXTj3ElOylg=@vger.kernel.org X-Gm-Message-State: AOJu0YxcHQwxWuSPFDi5ZeDssmWM5HxFrYk1bCLlo5jlGGNystcHEwg/ iuJ01PS/AcQ675oezjY46RPF2ozpAKmzVmR3JwBxV/4Fq8wCW6SxTWWKrXFwmbZW3mh0QuoQXDp xBEeIBVU+y54LvP4uFH/5YbmJBJfFuwZswk8O1tJ8/hHolU2IhoMty7uGOx2JgemPZXY= X-Gm-Gg: AfdE7cnKcakz0eKNQUt1nx2488yfgJk5Uu5aIJ2zskCrR3dpTGI6jCBwdDILIX+dpBu tuCGDgQW/B54ltnLwIzvX+b78Pggj3qGzqRrU6j6Z0IIgHsLN9aEfYz55u1/CzzV9nHXk92sG4R /XvJUHzoQuyVnc0o2CYtxNT640KA6y9tp1PcTDYjL6nlv/K0GeJmdcAJIsej8ABwtauxId1X7Pp JTsb+s4oc8bTYRC1cZhAk510qL9EBFsEEYqkqqUkHnJPOipPf80lxLIQD/pDijFLFXLjnodZ35w 9yv75nuQ6yd0WxvQyEh3dW6bxIwPxH4i/OhE4rfnq2Pf0Jx3WDnVg+I3eMvlVBmUOtZ2zmuE0Al d1s16umw4PdfQgthyHqtX2QqK5dwb79lNMCyoWz2Ci1xN0bvjRLRM40KKIAOc8Q== X-Received: by 2002:a05:6122:1c84:b0:573:a779:62cf with SMTP id 71dfb90a1353d-5bddf5980f2mr835730e0c.7.1782918409764; Wed, 01 Jul 2026 08:06:49 -0700 (PDT) X-Received: by 2002:a05:6122:1c84:b0:573:a779:62cf with SMTP id 71dfb90a1353d-5bddf5980f2mr835686e0c.7.1782918409349; Wed, 01 Jul 2026 08:06:49 -0700 (PDT) Received: from [192.168.69.212] (88-187-86-199.subs.proxad.net. [88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493be82fd71sm119405325e9.15.2026.07.01.08.06.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Jul 2026 08:06:48 -0700 (PDT) Message-ID: <8932ab7f-4547-4761-a9d5-04639727b79e@oss.qualcomm.com> Date: Wed, 1 Jul 2026 17:06:47 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 07/11] KVM: Initialize a vCPU's index to '-1' while it's being created Content-Language: en-US To: Sean Christopherson , Vitaly Kuznetsov , Paolo Bonzini , David Woodhouse , Paul Durrant Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+5b32c49cd8f005e65654@syzkaller.appspotmail.com, syzbot+5d2b94b77112148d1744@syzkaller.appspotmail.com, David Woodhouse References: <20260630225619.511632-1-seanjc@google.com> <20260630225619.511632-8-seanjc@google.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <20260630225619.511632-8-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-GUID: F0ZuZnq8thhCz3P9ULlwpVaSe2TM4s5W X-Authority-Analysis: v=2.4 cv=fLgJG5ae c=1 sm=1 tr=0 ts=6a452d0a cx=c_pps a=wuOIiItHwq1biOnFUQQHKA==:117 a=4s3hRJSeHn4rkQlkrse1kQ==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=M51BFTxLslgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=1XWaLZrsAAAA:8 a=EUspDBNiAAAA:8 a=LfsA7Cq2GQzuzbZ-N0YA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=XD7yVLdPMpWraOa8Un9W:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzAxMDE1OSBTYWx0ZWRfXyCG24HiDZBv/ OAnaXv3705LiLXTYoy5tMsC8vO2XHdcB7PmhmXyUGiwPT18gHewtsNnvT05uSE4cewtX/pqsssj KtFJbSYDvoosaNXJHYA+tdZ4g2u6rhh6XK9dZda/CfGQVxIr6d4D0hjiBttpMdjuOipQGbLn6MU 3e+4T0wqwVY/DallfIi19puTkgn+ujMQxQnXHMCQJRHqkbzUu90+pUzmjZ4p4tlTSc2jCFddYKA RcrBi4oIikjp82SLWtVYCbeuLIahoNhjClcG43IblRj5hGo+X9mAmD5Ef/n4QubGbKgGL4Mx89V nQ4/wvE80qJFymd5Xb0vtvvaPqYDmBi5Gidin3AfNa9h8kfDO74EqH0my9MerQiZiGO7BUUs+Nx bQ5je8gUCZ1livnG3fm6O/yfLqC17FgY0//Bk0K3au2rm7J4vlUDFYylyptMYMFExJfjCDtimo5 0kqbS97w1qd7IXnxOvQ== X-Proofpoint-ORIG-GUID: F0ZuZnq8thhCz3P9ULlwpVaSe2TM4s5W X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAxMDE1OSBTYWx0ZWRfX+bAfXuZHzNJu YXAN4L0G8T5q+aouiort43DctYPouTeFQT5GA8Dhs3elBS7vdY+vOd1xDqup0F/k60wv9zpST3b RUr5joIawdDmDtdufyYQQ9awbCswy6s= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-07-01_03,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 malwarescore=0 suspectscore=0 priorityscore=1501 bulkscore=0 spamscore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607010159 On 1/7/26 00:56, Sean Christopherson wrote: > Invalidate a vCPU's index immediately after allocating storage for the vCPU > so that KVM doesn't incorrectly treat a vCPU that is the process of being > created as being vCPU0. This will also allow detecting that a vCPU is in > the process of being created and thus otherwise unreachable, which is > useful for avoiding false positives in lockdep assertions on vcpu->mutex. > > Unwind the index back to -1 if inserting the vCPU into the array or adding > the vCPU to the fd table fails, so that kvm_arch_vcpu_destroy() sees the > vCPU as unreachable, i.e. so that teardown logic doesn't hit false positive > lockdep assertions. Opportunistically add a comment to call out that the > "real" index needs to be set before making the vCPU visible to other tasks. > > Note, kvm_wait_for_vcpu_online() naturally does the right thing thanks to > vcpu->vcpu_idx and kvm->online_vcpus being signed values. > > Signed-off-by: Sean Christopherson > --- > virt/kvm/kvm_main.c | 8 ++++++++ > 1 file changed, 8 insertions(+) Reviewed-by: Philippe Mathieu-Daudé