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[95.82.160.17]) by smtp.gmail.com with ESMTPSA id r2sm17134043wrv.39.2021.06.14.08.25.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jun 2021 08:25:21 -0700 (PDT) Subject: Re: [PATCH] block/nvme: Fix VFIO_MAP_DMA failed: No space left on device To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20210611114606.320008-1-philmd@redhat.com> From: =?UTF-8?B?TWljaGFsIFByw612b3puw61r?= Message-ID: <3d9db4c8-49f3-9313-ba6a-20e225eedcfb@redhat.com> Date: Mon, 14 Jun 2021 17:25:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210611114606.320008-1-philmd@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mprivozn@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=mprivozn@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.2, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.489, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , qemu-block@nongnu.org, qemu-stable@nongnu.org, Maxim Levitsky , Eric Auger , Alex Williamson , Stefan Hajnoczi , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/11/21 1:46 PM, Philippe Mathieu-Daudé wrote: > When the NVMe block driver was introduced (see commit bdd6a90a9e5, > January 2018), Linux VFIO_IOMMU_MAP_DMA ioctl was only returning > -ENOMEM in case of error. The driver was correctly handling the > error path to recycle its volatile IOVA mappings. > > To fix CVE-2019-3882, Linux commit 492855939bdb ("vfio/type1: Limit > DMA mappings per container", April 2019) added the -ENOSPC error to > signal the user exhausted the DMA mappings available for a container. > > The block driver started to mis-behave: > > qemu-system-x86_64: VFIO_MAP_DMA failed: No space left on device > (qemu) > (qemu) info status > VM status: paused (io-error) > (qemu) c > VFIO_MAP_DMA failed: No space left on device > qemu-system-x86_64: block/block-backend.c:1968: blk_get_aio_context: Assertion `ctx == blk->ctx' failed. > > Fix by handling the -ENOSPC error when DMA mappings are exhausted; > other errors (such -ENOMEM) are still handled later in the same > function. > > An easy way to reproduce this bug is to restrict the DMA mapping > limit (65535 by default) when loading the VFIO IOMMU module: > > # modprobe vfio_iommu_type1 dma_entry_limit=666 > > Cc: qemu-stable@nongnu.org > Reported-by: Michal Prívozník > Fixes: bdd6a90a9e5 ("block: Add VFIO based NVMe driver") > Buglink: https://bugs.launchpad.net/qemu/+bug/1863333 > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/65 > Signed-off-by: Philippe Mathieu-Daudé > --- > Michal, is it still possible for you to test this (old bug)? > Unfortunately I no longer have access to the machine. But, IIRC it was fairly easy to reproduce - just passthrough any NVMe disk using NVMe disk backend (-blockdev '{"driver":"nvme", ...). Sorry, Michal