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Tue, 15 Apr 2025 05:30:58 -0400 X-MC-Unique: d4kGaj37ME-eoeMkqpG0hw-1 X-Mimecast-MFC-AGG-ID: d4kGaj37ME-eoeMkqpG0hw_1744709456 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 87D5919560BB; Tue, 15 Apr 2025 09:30:55 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.133]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D28331808869; Tue, 15 Apr 2025 09:30:49 +0000 (UTC) Date: Tue, 15 Apr 2025 10:30:46 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Jonathan Cameron Cc: Shameer Kolothum , linuxarm@huawei.com, qemu-arm@nongnu.org, qemu-devel@nongnu.org, eric.auger@redhat.com, peter.maydell@linaro.org, jgg@nvidia.com, nicolinc@nvidia.com, ddutile@redhat.com, nathanc@nvidia.com, mochs@nvidia.com, smostafa@google.com, wangzhou1@hisilicon.com, jiangkunkun@huawei.com, zhangfei.gao@linaro.org Subject: Re: [PATCH 4/5] hw/arm/virt: Add support for smmuv3 device Message-ID: References: <20250415081104.71708-1-shameerali.kolothum.thodi@huawei.com> <20250415081104.71708-5-shameerali.kolothum.thodi@huawei.com> <20250415102542.00007fd7@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250415102542.00007fd7@huawei.com> User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org Sender: qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org X-TUID: p9JbXDpU3qUP On Tue, Apr 15, 2025 at 10:25:42AM +0100, Jonathan Cameron wrote: > On Tue, 15 Apr 2025 09:11:03 +0100 > Shameer Kolothum wrote: > > > Allow cold-plug of smmuv3 device to virt If the machine wide smmuv3 > > or a virtio-iommu is not specified. > > > > Also restrict the usage if virt <= 9.2. This will prevent accidently > > creating a SMMUv3 device on machines prior to 9.2 and cause failure > > on migrating to machines with same version but has a legacy smmuv3 > > device. > > Hi, > > As we discussed internally I'm not convinced we need to prevent this particular > way for a user to shoot themselves in the foot. > > To be a problem they have to specifically request an old machine + the > device that didn't exist for that machine, then migrate to a real old > version of QEMU. Agreed it is possible but I'm not sure we need to > prevent that particular crazy. Agreed, there are a million ways to screw up using old machine types with new features, so there's no compelling need to single out smmu for special protection in this respect. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|