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([2a0d:3344:2712:7e10:4d59:d956:544f:d65c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b61ca2b803sm12303133f8f.19.2025.07.22.00.37.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jul 2025 00:37:07 -0700 (PDT) Message-ID: <6a1e2b06-4f4f-45b7-8875-ecb60f74aa8d@redhat.com> Date: Tue, 22 Jul 2025 09:37:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 06/13] virtio-pci: implement support for extended features To: Jason Wang Cc: qemu-devel@nongnu.org, Paolo Bonzini , Dmitry Fleytman , Akihiko Odaki , Sriram Yagnaraman , "Michael S. Tsirkin" , Stefano Garzarella , Cornelia Huck , Luigi Rizzo , Giuseppe Lettieri , Vincenzo Maffione , Eric Blake , Markus Armbruster References: <253cd85bc76ded8259fc9d12ed3764e2507bcb75.1752828082.git.pabeni@redhat.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=pabeni@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.926, 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_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 On 7/22/25 5:28 AM, Jason Wang wrote: > On Fri, Jul 18, 2025 at 4:53 PM Paolo Abeni wrote: >> >> Extend the features configuration space to 128 bits, and allow the >> common read/write operation to access all of it. >> >> On migration, save the 128 bit version of the features only if the >> upper bits are non zero. Relay reset to clear all the feature >> space before load. >> >> Signed-off-by: Paolo Abeni > > This is a guest noticeable behaviour change. I wonder if we need a > command line option to enable and disable this feature for migration > compatibility. This point is not clear to me, could you please elaborate a bit more? do you mean we need i.e. a DEFINE_PROP_BOOL() or the like to enable the 128 bit space usage? Thanks, Paolo