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Tue, 6 Oct 2026 16:48:41 GMT Received: from smtprelay05.wdc07v.mail.ibm.com ([172.16.1.72]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 4h3eqyajap-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 06 Oct 2026 16:48:41 +0000 (GMT) Received: from smtpav01.wdc07v.mail.ibm.com (smtpav01.wdc07v.mail.ibm.com [10.39.53.228]) by smtprelay05.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 696GmdBU34144816 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 6 Oct 2026 16:48:39 GMT Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 98D6058059; Tue, 6 Oct 2026 16:48:39 +0000 (GMT) Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 874A958055; Tue, 6 Oct 2026 16:48:38 +0000 (GMT) Received: from [9.61.15.56] (unknown [9.61.15.56]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTP; Tue, 6 Oct 2026 16:48:38 +0000 (GMT) Message-ID: <50bca01c-e4aa-42ae-adc6-04e0b425d56d@linux.ibm.com> Date: Tue, 6 Oct 2026 12:48:38 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 15/17] s390x/pci: Provide each zpci device with a unique stable bus "path" To: Konstantin Shkolnyy Cc: alifm@linux.ibm.com, farman@linux.ibm.com, richard.henderson@linaro.org, iii@linux.ibm.com, david@kernel.org, cohuck@redhat.com, pasic@linux.ibm.com, borntraeger@linux.ibm.com, qemu-s390x@nongnu.org, qemu-devel@nongnu.org References: <20261006001643.420929-1-kshk@linux.ibm.com> <20261006001643.420929-16-kshk@linux.ibm.com> Content-Language: en-US From: Matthew Rosato In-Reply-To: <20261006001643.420929-16-kshk@linux.ibm.com> Content-Type: text/plain; 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envelope-from=mjrosato@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: qemu development 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 On 10/5/26 8:16 PM, Konstantin Shkolnyy wrote: > This is necessary for the follow-on migration support. The new unique > UID-based bus "path" is used as part of idstr in the migration stream, > making idstr unique and instance_id always 0. > > For migration to succeed, (idstr+instance_id) must match those generated > during QEMU start. Without unique idstr, QEMU will generate variable > instance_id to distinguish devices, and that instance_id can change > if a device is unplugged and plugged back, preventing migration. I suppose technically any pre-11.2 machine might not have this path, but at this point we don't even allow any zpci migration and won't allow zpci migration to any pre-11.2 machine with the next patch -- so that should be OK. Reviewed-by: Matthew Rosato