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(No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0BCA730BD1B4; Mon, 29 Jul 2019 21:37:35 +0000 (UTC) Received: from [10.18.17.74] (dhcp-17-74.bos.redhat.com [10.18.17.74]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1A3C65D9C5; Mon, 29 Jul 2019 21:37:32 +0000 (UTC) To: Paolo Bonzini , Stefan Hajnoczi References: <1562554503-177179-1-git-send-email-shaju.abraham@nutanix.com> <087e6cb5-b24d-b144-744c-d74defeadb86@redhat.com> <34a8030e-a173-162d-6786-3dafa5a1d4ed@redhat.com> <20190729100946.GC3369@stefanha-x1.localdomain> <9c34e70f-5ead-309c-865c-4a64d8a28724@redhat.com> <7005cc99-3bb2-fa70-aaf6-86870c37827b@redhat.com> From: John Snow Openpgp: preference=signencrypt Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef 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crash due to iSCSI Sense Key error 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: Kevin Wolf , shaju.abraham@nutanix.com, qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/29/19 5:32 PM, Paolo Bonzini wrote: > On 29/07/19 21:45, John Snow wrote: >> Next, we'll unschedule the BH if there is one. I think the only case >> where there is one is the reschedule_dma case of dma_blk_cb. (I'm not >> too familiar with these DMA helpers: in what cases do we expect the iov >> to be empty?) > > When there is another I/O that is using the DMA bounce buffer (the one > case that comes to mind in which you do DMA from MMIO areas is > loading/saving VGA RAM). > >> So it looks like this cancellation will produce one of two effects, >> depending on when it's invoked: >> >> 1) We'll stall the DMA permanently by deleting that BH, because >> dma_complete will never get invoked and therefore nobody will ever call >> ide_dma_cb with any return value of any kind. The IDE state machine >> likely just hangs waiting for the DMA to finish until the guest OS >> decides to reset the errant controller. >> >> 2) The DMA will continue blissfully unaware it was canceled, because the >> lower AIOCB has no cancel method, and so will finish, call back to >> dma_blk_cb, and continue the transfer loop unaware. >> >> >> ... Does your reading align with mine? >> >> >> If it does -- if there are indeed no places in the code today that >> artificially inject -ECANCELED -- I need to remove these special stanzas >> from the IDE code and allow the IDE state machine to handle these errors >> as true errors. > > The bug is that there is no place to inject -ECANCELED in the dbs->bh > case. I've sent an obviously^W untested patch. > Where does it inject -ECANCELED in the non-dbs->bh case? --js