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[80.230.79.166]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483bd70b3f3sm82558005e9.6.2026.02.25.07.15.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Feb 2026 07:15:19 -0800 (PST) Date: Wed, 25 Feb 2026 10:15:16 -0500 From: "Michael S. Tsirkin" To: Bertrand Marquis Cc: Parav Pandit , Manivannan Sadhasivam , "Bill Mills (bill.mills@linaro.org)" , "virtio-comment@lists.linux.dev" , "Edgar E . Iglesias" , Arnaud Pouliquen , Viresh Kumar , Alex Bennee , Armelle Laine Subject: Re: [PATCH v1 0/4] virtio-msg transport layer Message-ID: <20260225101404-mutt-send-email-mst@kernel.org> References: <359B0C17-9D57-423A-A229-6CEDA19C975A@arm.com> <02226901-7670-4AAB-8F55-0B2FB7C0CA49@arm.com> <20260225094902-mutt-send-email-mst@kernel.org> <8B4F5FE2-1F80-43BE-A60B-5C24B69C8B4E@arm.com> Precedence: bulk X-Mailing-List: virtio-comment@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4un2I2rrVfKJudmnufo8h6kBFi_4HYNf0KQg2E0aH1c_1772032521 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Feb 25, 2026 at 03:12:11PM +0000, Bertrand Marquis wrote: > Hi Parav, > > > On 25 Feb 2026, at 16:07, Parav Pandit wrote: > > > > Hi Bertrand, > > > >> From: Parav Pandit > >> Sent: 25 February 2026 08:30 PM > > > > [..] > >>>>>> So the PCI device is not one virtio device but one bus behind which there can be many devices. > >>>>>> > >>>>>> Is this making the concept a bit clearer ? > >>>>>> > >>>>> Yes. This makes a lot of sense now. > >>>>> > >>>>> This is a virtio-msg-transport device that needs its own device id in the table. > >>>>> And its binding to the PCI transport. > >>>> > >>>> ok. how about an rfc of that idea on the list? > >>> > >>> > >>> I will let Edgar answer on this. > >>> > >> Sure. > >> Also please explain how is this different than SR-IOV devices? > >> On a PCI device there are some child devices exposed using some virtio-msg bus transport. > >> And all of them are going to share same PCI BDF. > >> These individual devices cannot be mapped to different VMs (secure or regular) in a performant way either. > >> So what would this virtio-msg-transport device achieve? > >> > >> If there was no PCI bus when implementing the virtio-msg transport, it would make sense to avoid trap-emulate story. > >> But underlying transport being PCI, its back to square one for the originally described motivation. > > > > If the objective of the virtio-msg layer is to really support FF-A or similar other non-PCI transports, lets please focus the discussion on such use case and binding of that specific non-PCI bus. (like the link you pointed on arm site). > > > > This would help this series to progress faster without getting distracted on PCI side. > > Agree the example of virtio-msg over PCI made the discussion divert a bit. > > Maybe focusing on use cases like: > - FF-A > - messaging unit + shared memory > - hypervisor based events + shared memory > > > Would make the discussion focus more. > > Cheers > Bertrand > > indeed, possible. but do include ff-a bit for reference then. even if down the road it is not part of the spec (though no idea why and I would like to see). -- MST