From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 56B00476CFC for ; Fri, 11 Sep 2026 12:39:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789130381; cv=none; b=aw+xFCoLQJZ4ThXSLDPsEct0iXqpx+mElYNKaswNsSqhgUMe3A2ntbyFMKz2lwOzlv+1GBfog48VMdc/OuGbu0OcG6RPiAPi7cL32S3JvDbTrSNPDXrYdF6EkPQlwvJuNZfvzqO3ZnKqVh7JK3Pp7soGkieH1jD0m4zOfCI3gtY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789130381; c=relaxed/simple; bh=GDdmUOvL5qIET19hhzGDg8z0c0RlAlMuQVYPy1uq+Hw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YCbQQyoJzF9Jjw5rAxeiwvNB8x3adYgMap4ozYj5pYr+5KP5S28U6uzMdEEQ955O+Vj0lLyNRCGNCAFaWRsnCm0XU0OaU/f3hb6WkWzBENCMpg4l40webLxzCVerpasgsSSfdIr/daXlqb8DmO3SGili4i0fv0i2/OdMuugS6m0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=MxtqT1iy; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=gMfz6rRw; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MxtqT1iy"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="gMfz6rRw" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1789130373; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3o3AUP2GR4e8bKS56CF9rGMsnzBPpsvQ/7QSZVFmj6g=; b=MxtqT1iyLvIMbsg69wDC3iwbEuaPPQqn6okc4ie5s65UB2TMd0dGT0SNfMh/mc8yjMv/oO oV0s5uv70q2OK4rCuRoCbJjY2ApLy5PhJz7lY3//drmcc4pOhT6PPHN+oeRqDE/jyzh3R7 qFgUd9GVVjsxC7KYy6vczjR15DkHHoI= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-482-oqBlQUArMl--p9b32PGhkg-1; Fri, 11 Sep 2026 08:39:32 -0400 X-MC-Unique: oqBlQUArMl--p9b32PGhkg-1 X-Mimecast-MFC-AGG-ID: oqBlQUArMl--p9b32PGhkg_1789130371 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-49e661c6440so2199445e9.3 for ; Fri, 11 Sep 2026 05:39:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1789130371; x=1789735171; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=3o3AUP2GR4e8bKS56CF9rGMsnzBPpsvQ/7QSZVFmj6g=; b=gMfz6rRw+DBxRU4YO78zqKqIWImeitBaqF31uPDXFMaByCH8yHoXRrAj3JroA9oN84 SLx+bbW9/UPf4/8Hd9ch+NgwmlgzwlcxXVUw6FOYQ8Cz4Ru7oqR9jnshWW8zpa/zlTpn SjAP20UUp/cTbbIjE699Dh41l07Q/isXezQ5xIMAZmYuO2bVsJza6EL/xDTwujd8V2/q /onCMmHbVdYho0u2448KfoszrDucZJbicPUzxY5bteJne9p4mjgmwyd7ptzmjm/aadSS Od+VUBAbWX+Wcu5ZcsSk4YjdPMD0QKIJ5m0K4+S7Dpem5KZ+NgTRmkW2LL1a0+gzrUZ7 GUaw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789130371; x=1789735171; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=3o3AUP2GR4e8bKS56CF9rGMsnzBPpsvQ/7QSZVFmj6g=; b=WaPAHDVYvrLf1dtgpqvJPesjiMVLmbnlmwv+cWk8A6g2WhkKHFxb+4j6FjjZ1V6AjP CI3pDF7xZh9PmhssI+N+KyqHXp7z59vDrNBL7leMo7csh94YDZpLlkGq8RphbNXnbT1v Y9Ccqowf4HDDCrryL81uJF8SaY7SpYOQoh7YSJDtcwBrpVTsOuY3NddYAhBvr5GZO508 0jcKuTWrx/FjauEPyKA2Ti4AVcac9+B9rxTELCQXR5lElPoajtvL8gGsw+HDwLJpMmUO 53Y4mpl3ASIh6q0fsRIkfsB32gKeyhnqZj5FMkj2YC5a6fKHyl40AO3xDNUfql0GZv6b L8Wg== X-Forwarded-Encrypted: i=1; AKwUvBzm3YV0i+Xx4ac1otEavojmPEQizAAS3XEJzZrWJGy6/w3oGrQnJN+VVgzgsS5AC9bZNJz6aLhhWtoR@vger.kernel.org X-Gm-Message-State: AFuF++nTnR0+DDKTnmsx+DQxbC+nOsHcItxYk+q0n+TMEWHYqJLWP5tW 9tRAuwFIc4ky1czokfKIkYJVROhKyPOkJvmtiTChSblR3ojS+fdcE0+B6/Nfh6v/iAwfTOXE+tu SzpHnsHt/fAF68RtQ2z06jQn/MBbnpI910t2pfFxkjr4t9VVCdIDPiTBHM3qSXwE= X-Gm-Gg: AYBFou1v5R8UbqD2QYwsWiGVWMVYw3gOlKPbtShblUi310HJJ9V0x3x+y+go8EFcZRW NVfOgdAr6vNPtCLPEW4M157GmxIVyIowgroBJtIEXxkfFLlJz1FYJx0U+W5Mfy2T0DIAxr8PSLK jlxY5x83zGT8iXyQK5YftmJmHbGVSe+pI2kV+VXsEuRjEyNUx2FdoBPXLftfY9gk6A+f1V8GfA2 ikbEtZh8qg2epL+c1LUeb5tD914sxYPLQfru1NU1CLDg9Nf7hoF9s74lba4OEpUEBc/6i0lqJZQ zrJ0Gk0O/nKRXy35C9Xu2XPtK0gXd52YUz6xMgs5bJQoiMW2Xk1ZqnIakx7qCJgAPfDJ+TWDKL3 rIqiFZr6wNzvD3StFFumREEA= X-Received: by 2002:a05:600d:4452:20b0:499:b65d:124f with SMTP id 5b1f17b1804b1-49e6198c2aemr35358115e9.11.1789130370705; Fri, 11 Sep 2026 05:39:30 -0700 (PDT) X-Received: by 2002:a05:600d:4452:20b0:499:b65d:124f with SMTP id 5b1f17b1804b1-49e6198c2aemr35357705e9.11.1789130370161; Fri, 11 Sep 2026 05:39:30 -0700 (PDT) Received: from redhat.com (IGLD-80-230-79-236.inter.net.il. [80.230.79.236]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e6420de77sm22739175e9.3.2026.09.11.05.39.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Sep 2026 05:39:29 -0700 (PDT) Date: Fri, 11 Sep 2026 08:39:25 -0400 From: "Michael S. Tsirkin" To: Karl Mehltretter Cc: Jason Wang , Gerd Hoffmann , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Dmitry Torokhov , Rusty Russell , Pawel Moll , Cornelia Huck , Halil Pasic , Eric Farman , Richard Weinberger , Anton Ivanov , Johannes Berg , Hans de Goede , Ilpo =?iso-8859-1?Q?J=E4rvinen?= , Vadim Pasternak , Bjorn Andersson , Mathieu Poirier , virtualization@lists.linux.dev, linux-input@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-um@lists.infradead.org, platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/3] virtio: synchronize callbacks during device reset Message-ID: <20260911083848-mutt-send-email-mst@kernel.org> References: <20260905152059.89560-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260905152059.89560-1-kmehltretter@gmail.com> On Sat, Sep 05, 2026 at 05:20:56PM +0200, Karl Mehltretter wrote: > A virtqueue callback can outlive virtio_reset_device() and race with a > driver freeing the state it uses. The reset helper documents that no > callbacks remain in progress, but that depends on the transport: > virtio-pci waits in vp_reset(), while virtio-mmio does not. > > virtio_input has a related ordering problem: it unregisters the input > device before resetting the virtio device, while an event callback may > still be using the input device. > > Patch 1 moves the callback wait into the core, using the existing > virtio_synchronize_cbs() operation. Patch 2 fixes the virtio_input teardown > order. Patch 3 adds the missing synchronize_cbs hooks for UML, TmFIFO, > remoteproc and virtio-vdpa. Remoteproc uses one SRCU domain per processor. > > The new hooks wait for callbacks already running. UML, TmFIFO and > remoteproc still allow new callbacks after reset; fixing that is separate > work. The event-virtqueue DMA mapping issue is also separate. > > Changes in v2: > - Patch 1: move the wait into the core instead of fixing only MMIO, as > Michael suggested. Remove the duplicate PCI wait, preserve its shutdown > wait, and fix CCW callback locking. Drop the MMIO polling: reset polling > for v3 and newer is already in fa8833c085b6 ("virtio-mmio: add support > for transport version 3"). > - Patch 2: keep draining completed events when ready becomes false, > instead of breaking out, so teardown does not truncate an input packet. > - Patch 3 is new, at Michael's request. > > I reran the 120-cycle unbind/rebind test in an arm64 KASAN guest with four > vCPUs and a 5 ms busy delay per event. With patch 2 alone over virtio-mmio, > reset returned with the callback still running in all 84 overlapping > cycles. With the series, it waited in all 103. Over PCI with per-queue > MSI-X, it waited in all 66, including runs with threadirqs. No KASAN or > lockdep reports. These runs predate the per-rproc change, which leaves > the tested MMIO and PCI paths unchanged. They confirmed the missing wait, > but did not reproduce a use-after-free: with evdev attached, > input_unregister_device() waits for an RCU grace period that the IRQ > callback blocks. > > That version also passed QEMU input, rebind and shutdown checks on arm64 > MMIO and x86-64 PCI, including arm64 RT, KASAN and KCSAN builds, and x86 > UP/Tiny SRCU. A legacy INTx NIC was present for an additional x86 > shutdown check. The changed objects built with W=1 without warnings on > arm64, x86-64, s390 and SMP UML. The per-rproc version built with W=1 > on arm64 KASAN and x86 Tiny SRCU, and passed six remoteproc callback and > lifetime KUnit tests on each, using mock remoteproc devices. > > Link: https://lore.kernel.org/r/20260818040433.66986-1-kmehltretter@gmail.com I posted a version of patch 1, split up, just to give direction. Feel free to take over it, or test and ack. Thanks a lot for your work!