[{"id":3672378,"web_url":"http://patchwork.ozlabs.org/comment/3672378/","msgid":"<31ba8b4f-972c-4ec5-8366-8e668fef6a64@redhat.com>","list_archive_url":null,"date":"2026-04-01T17:34:40","subject":"Re: [PATCH 3/3] scsi: register again after PREEMPT without\n reservation","submitter":{"id":2701,"url":"http://patchwork.ozlabs.org/api/people/2701/","name":"Paolo Bonzini","email":"pbonzini@redhat.com"},"content":"On 4/1/26 19:19, Stefan Hajnoczi wrote:\n> The SCSI specification says PREEMPT without a reservation removes all\n> registrations with the given key. Try to register again after PREEMPT\n> since our key will have been removed.\n> \n> In practice some SCSI targets keep the calling I_T nexus' registration\n> instead of removing it. Therefore we need to handle both the\n> spec-compliant and the non-compliant behavior.\n> \n> Signed-off-by: Stefan Hajnoczi \n> ---\n> hw/scsi/scsi-generic.c | 10 ++++++++++\n> 1 file changed, 10 insertions(+)\n> \n> diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c\n> index 349dea6bdd..5182f9236d 100644\n> --- a/hw/scsi/scsi-generic.c\n> +++ b/hw/scsi/scsi-generic.c\n> @@ -513,6 +513,16 @@ bool scsi_generic_pr_state_preempt(SCSIDevice *s, Error **errp)\n> if (!scsi_generic_pr_preempt(s, key, resv_type, errp)) {\n> return false;\n> }\n> +\n> + /*\n> + * Some SCSI targets, like the Linux LIO target, remove our\n> + * registration when preempting without a reservation (resv_type is 0).\n> + * Try to register again but ignore the error since a RESERVATION\n> + * CONFLICT is expected if our registration remained in place.\n> + */\n> + if (resv_type == 0) {\n> + scsi_generic_pr_register(s, key, NULL);\n> + }\n\nHi Stefan,\n\nI'm replying here for both patch 2 and patch 3.\n\nCan this happen after the previous patch? (Also it's conflicting to say \n in patch 2 that LIO rejects PREEMPT, but also in this one that LIO \nunregisters the key).\n\nAnd for patch 2, is a RELEASE needed after issuing PREEMPT with an \nartificial PR_TYPE_WRITE_EXCLUSIVE?\n\nPaolo","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=OKC+UFqE;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fmBwl3zwzz1yCp\n\tfor ; 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keydata=\n xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2\n CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04\n hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX\n DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S\n P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU\n Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo\n UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC\n tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd\n wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j\n UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH\n CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E\n 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj\n jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0\n VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K\n CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG\n SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9\n AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE\n AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB\n nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr\n bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl\n KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF\n m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk\n tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF\n dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP\n JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp\n sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD\n OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM\n GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN\n Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d\n usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL\n xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0\n JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP\n dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh\n b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w=","In-Reply-To":"<20260401171927.396672-4-stefanha@redhat.com>","Content-Type":"text/plain; charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","X-Scanned-By":"MIMEDefang 3.0 on 10.30.177.12","Received-SPF":"pass client-ip=170.10.133.124;\n envelope-from=pbonzini@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com","X-Spam_score_int":"-6","X-Spam_score":"-0.7","X-Spam_bar":"/","X-Spam_report":"(-0.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.01,\n RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=1, RCVD_IN_VALIDITY_RPBL_BLOCKED=1,\n SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"}},{"id":3672398,"web_url":"http://patchwork.ozlabs.org/comment/3672398/","msgid":"<20260401183057.GA400282@fedora>","list_archive_url":null,"date":"2026-04-01T18:30:57","subject":"Re: [PATCH 3/3] scsi: register again after PREEMPT without\n reservation","submitter":{"id":17227,"url":"http://patchwork.ozlabs.org/api/people/17227/","name":"Stefan Hajnoczi","email":"stefanha@redhat.com"},"content":"On Wed, Apr 01, 2026 at 07:34:40PM +0200, Paolo Bonzini wrote:\n> On 4/1/26 19:19, Stefan Hajnoczi wrote:\n> > The SCSI specification says PREEMPT without a reservation removes all\n> > registrations with the given key. Try to register again after PREEMPT\n> > since our key will have been removed.\n> > \n> > In practice some SCSI targets keep the calling I_T nexus' registration\n> > instead of removing it. Therefore we need to handle both the\n> > spec-compliant and the non-compliant behavior.\n> > \n> > Signed-off-by: Stefan Hajnoczi \n> > ---\n> > hw/scsi/scsi-generic.c | 10 ++++++++++\n> > 1 file changed, 10 insertions(+)\n> > \n> > diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c\n> > index 349dea6bdd..5182f9236d 100644\n> > --- a/hw/scsi/scsi-generic.c\n> > +++ b/hw/scsi/scsi-generic.c\n> > @@ -513,6 +513,16 @@ bool scsi_generic_pr_state_preempt(SCSIDevice *s, Error **errp)\n> > if (!scsi_generic_pr_preempt(s, key, resv_type, errp)) {\n> > return false;\n> > }\n> > +\n> > + /*\n> > + * Some SCSI targets, like the Linux LIO target, remove our\n> > + * registration when preempting without a reservation (resv_type is 0).\n> > + * Try to register again but ignore the error since a RESERVATION\n> > + * CONFLICT is expected if our registration remained in place.\n> > + */\n> > + if (resv_type == 0) {\n> > + scsi_generic_pr_register(s, key, NULL);\n> > + }\n> \n> Hi Stefan,\n> \n> I'm replying here for both patch 2 and patch 3.\n> \n> Can this happen after the previous patch? (Also it's conflicting to say in\n> patch 2 that LIO rejects PREEMPT, but also in this one that LIO unregisters\n> the key).\n\nYes. Both patches are needed.\n\nThe first patch gets LIO to process the PREEMPT. Before LIO would just\nfail the command.\n\nBut once LIO processes the PREEMPT, we hit the next problem: PREEMPT\ncompletes but our registration has been removed. So now we need to\nregister again after PREEMPT.\n\n> And for patch 2, is a RELEASE needed after issuing PREEMPT with an\n> artificial PR_TYPE_WRITE_EXCLUSIVE?\n\nNo, because PREEMPT will not acquire a reservation when there is no\nreservation holder with the given key. PREEMPT will only remove\nregistrations in that case.\n\nStefan","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=CCgzCYPx;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fmF5h1DbVz1xtJ\n\tfor ; Thu, 02 Apr 2026 06:14:00 +1100 (AEDT)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1w810Z-0003RK-3t; 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Wed, 1 Apr 2026 18:31:00 +0000 (UTC)","from localhost (unknown [10.44.32.12])\n by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP\n id 520DF1800671; Wed, 1 Apr 2026 18:30:58 +0000 (UTC)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1775068266;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n in-reply-to:in-reply-to:references:references;\n bh=5qPEIJ870NSeuHpii3DCPuBaCM6n8ZznzPXviE/dGVA=;\n b=CCgzCYPx6zcvFBEWWiQfWfpv6M0FKB1mA5CDYZN6hnUWpCdOwOkRc2+7QNid2WwSUgevJ6\n osDol2PYwO6GtIAqm508sFDDYur4EIZaUJ5ZBCt494vHQeKtBzzoAFRihpsein4Q1/Bu1l\n DzxRpf0g/s24HXtHvehAhceXsUaFvBs=","X-MC-Unique":"sHOs8MCKMn6QMlAcSrdfXw-1","X-Mimecast-MFC-AGG-ID":"sHOs8MCKMn6QMlAcSrdfXw_1775068261","Date":"Wed, 1 Apr 2026 14:30:57 -0400","From":"Stefan Hajnoczi ","To":"Paolo Bonzini ","Cc":"qemu-devel@nongnu.org, qemu-stable@nongnu.org, qemu-block@nongnu.org,\n Fam Zheng ","Subject":"Re: [PATCH 3/3] scsi: register again after PREEMPT without\n reservation","Message-ID":"<20260401183057.GA400282@fedora>","References":"<20260401171927.396672-1-stefanha@redhat.com>\n <20260401171927.396672-4-stefanha@redhat.com>\n <31ba8b4f-972c-4ec5-8366-8e668fef6a64@redhat.com>","MIME-Version":"1.0","Content-Type":"multipart/signed; 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Before LIO would just\n> fail the command.\n>\n> But once LIO processes the PREEMPT, we hit the next problem: PREEMPT\n> completes but our registration has been removed. So now we need to\n> register again after PREEMPT.\n>\n> > And for patch 2, is a RELEASE needed after issuing PREEMPT with an\n> > artificial PR_TYPE_WRITE_EXCLUSIVE?\n>\n> No, because PREEMPT will not acquire a reservation when there is no\n> reservation holder with the given key. PREEMPT will only remove\n> registrations in that case.\n\nThanks for explaining all this. I didn't understand the behavior where\nthe source does not have a reservation. Series\n\nReviewed-by: Paolo Bonzini \n\nPaolo","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=X2BzbFnM;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=lQGekknu;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fmdfb0WpNz1yCs\n\tfor ; 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