From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <010701a169c648ab-378b693f-0a8a-49b2-a9a0-51dd480af434-000000@eu-central-1.amazonses.com> Received: from AM0PR02CU008.outbound.protection.outlook.com (mail-westeuropeazon11023115.outbound.protection.outlook.com [52.101.72.115]) by lore.virtuozzo.com (Postfix) with ESMTPS id BBA308017D for ; Fri, 23 Oct 2026 17:19:28 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=onKY6IePDGSwmUuq2scct0H8pXG6Q9Pq4JUVgxqD8lFScW90xx+2MhHR1cAdjHY/7eG6jFcoRf2+f+a+f5lzrZeRWURBcBAejS6vATs9bHFtirFLaVZj1Ha5Y6FthhNegRMxuCBbzq/Q+PfUE76Sjf0gusdNdUcmvv35ONUMd2qUgDSSeHk/GtWSu/PRKjM0CINla/jYLa42+yjjwQyIj6xKT3w3eIl3XiH324TzS2f+S2uw1WZQ3Z5moqXWlMaFdjOBgpf1LU3QSdXVP5EjSJzZXkHCXyU9hzv0HAlsVXDd70v5ze0zB71wUyIYMImFfk2mZCX3ytfzO7hFz1S/eg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=55rdGEwlLiYjx8dNWFtnO/9QYfgHd4y8iWDH5Z/zt1o=; b=QJLt0Sqq993EGnXqFC/rzGzzmRgfqjQ8+ygtNj9R6hwmDLMdvVY53nyPVzfzZ/8kvHrbMB6WVQcCzoljS9B0Dp2pX2DzwrFFSOedOGmqRR12QHAdLj6PoPa6pfaj8a2I2VUixUEig00B3hLelUbJqZoPHwZikTokoRB7eQPlmCPFAXWtBalg+VDwDZRyV17/+svWPgb/uMuExZSj3OdzoizTamZT2IF9jJzewixn+QFBIEWi9HuNTJ1StM02rua96i/bcQKGuhV1PTXFf+RVrd+/lXSPR80cxbpEPYO09ijjPXtnvYReII9nSazEqZmxua2qv8Tooh/b7JZsDNGY3w== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 69.169.224.1) smtp.rcpttodomain=virtuozzo.com smtp.mailfrom=eu-central-1.amazonses.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=sashiko.virtuozzo.com; dkim=pass (signature was verified) header.d=sashiko.virtuozzo.com; dkim=pass (signature was verified) header.d=amazonses.com; arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.onmicrosoft.com; s=selector2-virtuozzo-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=55rdGEwlLiYjx8dNWFtnO/9QYfgHd4y8iWDH5Z/zt1o=; b=orDKsZ2834ZEAiq4FWYtWL6umOLADJzx1JT1ZKLhFU8pF/jqOLYR3Wi5jKSB+2ASq/o7rbmXsyRsGnnCftiiy5gF9xo0ecwEv0Vd0wzlBs60s1SrwTcUrIjaBS4ea8at5M023K/gcNOdjKqe4RznzMDjHa38I+30iIJNBSs/Mi8= Received: from DU2PR04CA0232.eurprd04.prod.outlook.com (2603:10a6:10:2b1::27) by AS2PR08MB10252.eurprd08.prod.outlook.com (2603:10a6:20b:648::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.546.18; Fri, 23 Oct 2026 17:19:25 +0000 Received: from DU2PEPF00028D07.eurprd03.prod.outlook.com (2603:10a6:10:2b1:cafe::82) by DU2PR04CA0232.outlook.office365.com (2603:10a6:10:2b1::27) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.21.546.19 via Frontend Transport; Fri, 23 Oct 2026 17:19:25 +0000 Authentication-Results: mx.microsoft.com 1; spf=pass (sender IP is 69.169.224.1) smtp.mailfrom=eu-central-1.amazonses.com; dkim=pass (signature was verified) header.d=sashiko.virtuozzo.com;dkim=pass (signature was verified) header.d=amazonses.com;dmarc=pass action=none header.from=sashiko.virtuozzo.com; Received-SPF: Pass (protection.outlook.com: domain of eu-central-1.amazonses.com designates 69.169.224.1 as permitted sender) receiver=protection.outlook.com; client-ip=69.169.224.1; helo=b224-1.smtp-out.eu-central-1.amazonses.com; pr=C Received: from b224-1.smtp-out.eu-central-1.amazonses.com (69.169.224.1) by DU2PEPF00028D07.mail.protection.outlook.com (10.167.242.167) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.21.546.15 via Frontend Transport; Fri, 23 Oct 2026 17:19:25 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=23yjbh4k34hwzfubhuiim7m4inbd3ick; d=sashiko.virtuozzo.com; t=1792775965; h=Message-ID:From:Subject:To:In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=BsBXHe0cyUajqYyHmDiUl63rl4E0w0lzsSqHLROLSgQ=; b=2AaoLjhCztqyG41NXsV9m3RrlMkQ8thT7m1UBH5A8WfNuq8F95THhUi6lFw3diJ+ o0A3ySnSxxmroFvIY/7ZWZr7bcfVyjQFW39fai6kXzroHtdshhWqWPpH5kAjpSSX05T 8lxJj/X+YBFMl1widVZxUj+tlbz1ex5+4o/+lhvw1bpL5Lg3Ewm4AcIRMv/0lLDLqqQ xkfYtAE9A0bpu1Y+NDkHj+1hw9GKg82kDr8zOaGex8JuVTAPM2RdURDxWn34eNA/aUB dXsvbdQpDm96vOtoMN+DKnXu9NbMrnfWCOGygyx6zexdYNq/9IkaEPdEsu7XJuXKNmZ XEsV/QAIsQ== DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=qftdzk2dqsatjnlrq4r5brjbihpfcrsh; d=amazonses.com; t=1792775965; h=Message-ID:From:Subject:To:In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date:Feedback-ID; bh=BsBXHe0cyUajqYyHmDiUl63rl4E0w0lzsSqHLROLSgQ=; b=a6f5N85phvAmCkdV2KYqiLuy6n8giwjn34RgJvhI5Y6JCN4jtCVHj+UzQ1UKhs1B V7T5ojIFxJhmwR5pMNNijkZ79sqrbP75JA5lNV9JACqUYIvPdiy7pgm4y9hZjHsGe4s y7TSAkvY0u6D5nwLdjoHlV7bohblxgIKL2eL0Mdg= Message-ID: <010701a169c648ab-378b693f-0a8a-49b2-a9a0-51dd480af434-000000@eu-central-1.amazonses.com> From: no-reply@sashiko.virtuozzo.com Subject: Re: [PATCH QEMU HCI-8.1 v5 23/36] kvm: fix coalesced MMIO flush racing with kvm_close() To: svt-core@virtuozzo.com, Andrey Drobyshev In-Reply-To: <20261023-vfio_v1-v5-23-ba0bf3c6d122@virtuozzo.com> References: <20261023-vfio_v1-v5-0-ba0bf3c6d122@virtuozzo.com> <20261023-vfio_v1-v5-23-ba0bf3c6d122@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 23 Oct 2026 17:19:24 +0000 Feedback-ID: ::1.eu-central-1.2wRQJBpg9g1fGRYexx3dUuYGS25Bux+2TEOx72/m6U4=:AmazonSES X-SES-Outgoing: 2026.10.23-69.169.224.1 X-EOPAttributedMessage: 0 X-EOPTenantAttributedMessage: 0bc7f26d-0264-416e-a6fc-8352af79c58f:0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DU2PEPF00028D07:EE_|AS2PR08MB10252:EE_ MIME-Version: 1.0 X-MS-Office365-Filtering-Correlation-Id: 841eeb83-e051-487f-e425-08df3129c987 X-LD-Processed: 0bc7f26d-0264-416e-a6fc-8352af79c58f,ExtAddr X-MS-Exchange-AtpMessageProperties: SA List-Id: svt-core@virtuozzo.com X-MS-Exchange-Transport-Rules-Loop: 1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|48200799018|376014|61400799027|32142699015|9140799003|4143699003|56012099006|5063699009|5023799004|261022105027099003|261022075727099003|261009223027099003|261021121427099003|10067099003|16102099003|22082099003|55112099003|4113699003|5113699003|18002099003|13003099007; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:69.169.224.1;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:b224-1.smtp-out.eu-central-1.amazonses.com;PTR:b224-1.smtp-out.eu-central-1.amazonses.com;CAT:NONE;SFS:(13230040)(48200799018)(376014)(61400799027)(32142699015)(9140799003)(4143699003)(56012099006)(5063699009)(5023799004)(261022105027099003)(261022075727099003)(261009223027099003)(261021121427099003)(10067099003)(16102099003)(22082099003)(55112099003)(4113699003)(5113699003)(18002099003)(13003099007);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: cqzzXCL0dUDFCqkstaXWJ6KixaB0ymkMM6m3PAK5soHR56eFdkGEPiMvQDQ3WTsz8MtKeB1eg2caIxuAJTQGr2zyxm63vRZ3NKsmLqgZGu3v4s8W83LmEb6YKme5amglvNVtvIwiEhv26MxL24soDnZuQydXug/fDFGsil36YeeCfIhTP0NnvSDXi9/rfccduPEifXeg0GPXWRBXbt9rW0qXzYz1JIP5hLCRUN+78t9rGn/8PQmD5y0iPULYftc0Jriwmkt1Yct7bE2Ssda6MQVb4EsQMwrr2w9kXtyjtxqWVGtl5mxgdBAU0hBpQln8ZWQCiHXoUpd0vTRs97aRfZ3wtUggr/GKlYpIR3cEsqLIEIc2K5YeQTGK2cKz+7+FOnNaovv531a3PQtLrE+slMi3WLGLA6Lc/YB9+ue90x1YLqkXmph7J0sW2jGlc7Pt X-ExternalRecipientOutboundConnectors: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Oct 2026 17:19:25.3562 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 841eeb83-e051-487f-e425-08df3129c987 X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-CrossTenant-AuthSource: DU2PEPF00028D07.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: Internet X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS2PR08MB10252 > kvm_close() destroys the vCPUs, which unmaps their kvm_run areas, and the > coalesced MMIO ring lives in the kvm_run area of the first vCPU. Nothing > stops the RCU thread from flushing that ring at the same time: finalizing > a memory region of a freed flatview calls memory_region_transaction_begin= () > and thus kvm_flush_coalesced_mmio_buffer(). kvm_state is still set at > that point, so the flush reads the ring after it has been unmapped: >=20 > #0 kvm_flush_coalesced_mmio_buffer accel/kvm/kvm-all.c > #1 qemu_flush_coalesced_mmio_buffer > #2 memory_region_transaction_begin > #3 memory_region_finalize > ... > #10 flatview_destroy > #11 call_rcu_thread >=20 > while the main thread is in: >=20 > kvm_close -> cpu_remove_sync > vfio_kvm_device_close > vfio_cpr_kvm_close_notifier (MIG_EVENT_PRECOPY_DONE) >=20 > Seen as a SIGSEGV of the old QEMU during repeated cpr-exec of a VM with > a VFIO device. >=20 > Clear the ring pointer first, so that new flushes skip it, and wait for > the pending RCU callbacks before destroying the vCPUs. >=20 > Fixes: 7ed0919119b0 ("migration: close kvm after cpr") > Signed-off-by: Andrey Drobyshev Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.vzint.dev/#/patchset/20261023-vfio= _v1-v5-0-ba0bf3c6d122@virtuozzo.com?part=3D23