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Thu, 3 Feb 2022 22:28:34 -0800 (PST) Message-ID: <2bbed027-b9a1-e5db-3a3d-90c40af49e09@opensource.wdc.com> Date: Fri, 4 Feb 2022 15:28:33 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 To: Chaitanya Kulkarni , Adam Manzanares References: <20220201102122.4okwj2gipjbvuyux@mpHalley-2> <270f30df-f14c-b9e4-253f-bff047d32ff0@nvidia.com> <20220203153843.szbd4n65ru4fx5hx@garbanzo> <20220203165238.GA142129@dhcp-10-100-145-180.wdc.com> <20220203195155.GB249665@bgt-140510-bm01> <863d85e3-9a93-4d8c-cf04-88090eb4cc02@nvidia.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <863d85e3-9a93-4d8c-cf04-88090eb4cc02@nvidia.com> X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-loop: dm-devel@redhat.com Cc: "djwong@kernel.org" , "linux-nvme@lists.infradead.org" , "clm@fb.com" , "dm-devel@redhat.com" , "osandov@fb.com" , =?UTF-8?Q?Javier_Gonz=c3=a1lez?= , Bart Van Assche , "linux-scsi@vger.kernel.org" , Christoph Hellwig , "roland@purestorage.com" , "zach.brown@ni.com" , "dsterba@suse.com" , "msnitzer@redhat.com >> msnitzer@redhat.com" , "josef@toxicpanda.com" , "linux-block@vger.kernel.org" , Mikulas Patocka , Keith Busch , "Frederick.Knight@netapp.com" , Jens Axboe , "tytso@mit.edu" , Kanchan Joshi , "martin.petersen@oracle.com >> Martin K. Petersen" , Luis Chamberlain , "jack@suse.com" , linux-fsdevel , "lsf-pc@lists.linux-foundation.org" Subject: Re: [dm-devel] [RFC PATCH 3/3] nvme: add the "debug" host driver X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On 2/4/22 12:12, Chaitanya Kulkarni wrote: > >>>> One can instantiate scsi devices with qemu by using fake scsi devices, >>>> but one can also just use scsi_debug to do the same. I see both efforts >>>> as desirable, so long as someone mantains this. >>>> > > Why do you think both efforts are desirable ? When testing code using the functionality, it is far easier to get said functionality doing a simple "modprobe" rather than having to setup a VM. C.f. running blktests or fstests. So personally, I also think it would be great to have a kernel-based emulation of copy offload. And that should be very easy to implement with the fabric code. Then loopback onto a nullblk device and you get a quick and easy to setup copy-offload device that can even be of the ZNS variant if you want since nullblk supports zones. > > NVMe ZNS QEMU implementation proved to be perfect and works just > fine for testing, copy offload is not an exception. > >>>> For instance, blktests uses scsi_debug for simplicity. >>>> >>>> In the end you decide what you want to use. >>> >>> Can we use the nvme-loop target instead? >> >> I am advocating for this approach as well. It presentas a virtual nvme >> controller already. >> > > It does that assuming underlying block device such as null_blk or > QEMU implementation supports required features not to bloat the the > NVMeOF target. > > -ck > > -- Damien Le Moal Western Digital Research -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel