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Tsirkin" To: David Hildenbrand Cc: Halil Pasic , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, Chandra Merla , Stable@vger.kernel.org, Cornelia Huck , Thomas Huth , Eric Farman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Wei Wang Subject: Re: [PATCH v1] s390/virtio_ccw: don't allocate/assign airqs for non-existing queues Message-ID: <20250407044246-mutt-send-email-mst@kernel.org> References: <4a33daa3-7415-411e-a491-07635e3cfdc4@redhat.com> <20250404153620.04d2df05.pasic@linux.ibm.com> <20250404160025.3ab56f60.pasic@linux.ibm.com> <6f548b8b-8c6e-4221-a5d5-8e7a9013f9c3@redhat.com> <20250404173910.6581706a.pasic@linux.ibm.com> <20250407034901-mutt-send-email-mst@kernel.org> <2b187710-329d-4d36-b2e7-158709ea60d6@redhat.com> <39a67ca9-966b-40c1-b080-95d8e2cde376@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <39a67ca9-966b-40c1-b080-95d8e2cde376@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: _iUMUHFdyuF0RAoEBmFP05t7PAvo1Xhi1BbaZ9Cuo0g_1744015476 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Wow great job digging through all these hypervisors! On Mon, Apr 07, 2025 at 10:38:59AM +0200, David Hildenbrand wrote: > crossvm: > https://github.com/google/crosvm/blob/main/devices/src/virtio/balloon.rs > > -> Hard-codes queue numbers; does *not* offer/implement > VIRTIO_BALLOON_F_STATS_VQ but does offer VIRTIO_BALLOON_F_STATS_VQ > and VIRTIO_BALLOON_F_DEFLATE_ON_OOM. > > -> Implements something that is not in the virtio-spec > > const VIRTIO_BALLOON_F_WS_REPORTING: u32 = 8; // Working Set Reporting > virtqueues > > and > > const WS_DATA_VQ: usize = 5; > const WS_OP_VQ: usize = 6; > > > IIUC, Linux inside cross-vm might actually be problematic? They would > disagree on the virtqueue for free-page-reporting That's why things must be tied to negotiated features, not to offered ones. > > Maybe I am missing something, it's a mess ... Indeed. Let's fix the implementations while keeping work arounds for existing ones. -- MST