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Mon, 24 Aug 2026 22:00:16 GMT Received: from smtprelay03.wdc07v.mail.ibm.com ([172.16.1.70]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 4g7rsy0fqf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 24 Aug 2026 22:00:16 +0000 (GMT) Received: from smtpav04.dal12v.mail.ibm.com (smtpav04.dal12v.mail.ibm.com [10.241.53.103]) by smtprelay03.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 67OLxY7j28705504 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 24 Aug 2026 21:59:35 GMT Received: from smtpav04.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 86F5A5805A; Mon, 24 Aug 2026 22:00:14 +0000 (GMT) Received: from smtpav04.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C1F7E58052; Mon, 24 Aug 2026 22:00:13 +0000 (GMT) Received: from [9.61.21.147] (unknown [9.61.21.147]) by smtpav04.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 24 Aug 2026 22:00:13 +0000 (GMT) Message-ID: <31f8a6a3-073e-4d84-b743-906e0a6f85f1@linux.ibm.com> Date: Mon, 24 Aug 2026 18:00:13 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 13/15] s390x/pci: Add a comment explaining S390PCIIOMMU purpose 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: <20260818172521.223460-1-kshk@linux.ibm.com> <20260818172521.223460-14-kshk@linux.ibm.com> Content-Language: en-US From: Matthew Rosato In-Reply-To: <20260818172521.223460-14-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 8/18/26 1:25 PM, Konstantin Shkolnyy wrote: > Because S390PCIIOMMU has just been cleaned up of fields it didn't have to > carry, add a comment explaining why it exists in the first place and > discouraging adding more fields to it in the future. In following the theme with the other patches, how about a re-word to something like: Now that S390PCIIOMMU had been reduced to only the IOMMU container information needed by the PCI layer for the associated slot, add a comment explaining the purpose of the structure. > > Signed-off-by: Konstantin Shkolnyy > --- > include/hw/s390x/s390-pci-bus.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h > index e3cbee2695..17ecf3e0da 100644 > --- a/include/hw/s390x/s390-pci-bus.h > +++ b/include/hw/s390x/s390-pci-bus.h > @@ -271,6 +271,17 @@ typedef struct S390PCIDMACount { > QTAILQ_ENTRY(S390PCIDMACount) link; > } S390PCIDMACount; > > +/* > + * This structure holds the PCI device AddressSpace that QEMU needs to link > + * into its internal structures before the zPCI and PCI devices are fully > + * initialized. QEMU wants to have this "root" AddressSpace before the PCI > + * device is plugged in. It's only actually used for I/O while the PCI > + * device is plugged in and configured by the guest, at which time it has > + * additional memory subregions from zPCI device, that can do real work. > + * In other words, S390PCIIOMMU holds fields that logically belong to > + * S390PCIBusDevice but need to exist before S390PCIBusDevice exists. > + * Therefore, no other kind of fields should be placed in S390PCIIOMMU. > + */ Starting from "In other words," your comment gets inaccurate. We will actually ensure that a S390PCIBusDevice is either 1) already created prior to the PCIDevice or 2) will create it on-demand during s390_pcihost_plug() for TYPE_PCI_DEVICE if it didn't already exist. This nuance goes back to my comment earlier about the lifecycle being a bit odd. For now I would suggest to just drop the last 3 lines starting with "In other words, ..." With those 3 lines removed and the commit message re-worded: Reviewed-by: Matthew Rosato