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Tue, 2 Jul 2024 14:55:42 -0400 (EDT) Date: Tue, 2 Jul 2024 20:55:37 +0200 From: Klaus Jensen To: Keith Busch Cc: Ayush Mishra , qemu-devel@nongnu.org, foss@defmacro.it Subject: Re: [PATCH] hw/nvme: actually implement abort Message-ID: References: <20240702080232.848849-1-ayush.m55@samsung.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="iawZ6SKbd08+BDln" Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=103.168.172.147; envelope-from=its@irrelevant.dk; helo=fout4-smtp.messagingengine.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --iawZ6SKbd08+BDln Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Jul 2 09:24, Keith Busch wrote: > On Tue, Jul 02, 2024 at 01:32:32PM +0530, Ayush Mishra wrote: > > Abort was not implemented previously, but we can implement it for AERs = and asynchrnously for I/O. >=20 > Not implemented for a reason. The target has no idea if the CID the > host requested to be aborted is from the same context that the target > has. Target may have previoulsy completed it, and the host re-issued a > new command after the abort, and due to the queueing could have been > observed in a different order, and now you aborted the wrong command. I might be missing something here, but are you saying that the Abort command is fundamentally flawed? Isn't this a host issue? The Abort is for a specific CID on a specific SQID. The host *should* not screw this up and reuse a CID it has an outstanding Abort on? I don't think there are a lot of I/O commands that a host would be able to cancel (in QEMU, not at all, because only the iscsi backend actually implements blk_aio_cancel_async). But some commands that issue multiple AIOs, like Copy, may be long running and with this it can actually be cancelled. And with regards to AERs, I don't see why it is not advantageous to be able to Abort one? --iawZ6SKbd08+BDln Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEUigzqnXi3OaiR2bATeGvMW1PDekFAmaETSgACgkQTeGvMW1P DekELwgAuL15MnrD/HOtGQWf7Tjrn8gau2LUKxAtoX7PgvWeznKFMdlewB+ActAl yaEHFGCS/A0hHl3udLVE5oI9cSQFlLSLeNzsl4Ua8zazNLpdB7fJWy6+1fb/mNx2 RwB36kj/K5oHZUDYntg0Z6K0IlLAXw4vypfk0yUqLu2BaEEqh/6A1xN5s28zxgi8 as7mXX/jvZWaa2nmU+znx4ZC1EHAa2H84st6soZKjTp6r+y8G/Ii7Smlu05Z6TPV YEcIKGTdFvOzO2cifRHc2sE2r0i6NTsPKE/xaQ2kx3rTEBg0Z/QvXI9qNEYoTqLO O4tdv93s7TaxTc2fAyScJ47RaBa/gg== =agQ5 -----END PGP SIGNATURE----- --iawZ6SKbd08+BDln--