From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Parav Pandit Subject: RE: [PATCH 2/5] Introduce VIRTIO_F_ADMIN_VQ_INDIRECT_DESC/VIRTIO_F_ADMIN_VQ_IN_ORDER Date: Tue, 18 Jan 2022 10:50:52 +0000 Message-ID: References: <20220113121203-mutt-send-email-mst@kernel.org> <20220117170442-mutt-send-email-mst@kernel.org> <20220118011731-mutt-send-email-mst@kernel.org> <20220118014737-mutt-send-email-mst@kernel.org> <20220118020831-mutt-send-email-mst@kernel.org> <20220118052715-mutt-send-email-mst@kernel.org> In-Reply-To: <20220118052715-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable To: "Michael S. Tsirkin" Cc: Max Gurtovoy , "virtio-comment@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-dev@lists.oasis-open.org" , "jasowang@redhat.com" , Shahaf Shuler , Oren Duer , "stefanha@redhat.com" List-ID: > From: Michael S. Tsirkin > Sent: Tuesday, January 18, 2022 4:09 PM >=20 > On Tue, Jan 18, 2022 at 07:30:34AM +0000, Parav Pandit wrote: > > An unrelated command to AQ in Jason's proposal [1] is about " The > management driver MUST create a managed device by allocating". > > We see that creator of the subfunction is often not the only entity man= aging > it. > > They being same in new era finding less and less users. > > So this piece needs more discussion whenever we address that. > > > > [1] > > https://lists.oasis-open.org/archives/virtio-comment/202108/msg00136.h > > tml >=20 > This reminds me. How do AQ commands interact with VF lifecycle? VF device usage is controlled by the same system which is configuring the V= F via its parent PF device. So VF device shouldn't be in use. Any configuration change while VF device = is in use will result in failing the AQ command. > E.g. can one change number of vectors for an active VF? > Need to specify this. >=20 > Also, I started worrying about compatibility here. > Let's say the msix capability in a VF specifies 16 vectors. > Can PF specify 32? If yes how will driver program them? Yes, PF can change to 32. When VF driver queries the PCI capability, it wil= l reflect 32 instead of 16. > Can PF specify 8? If yes how do we make sure driver does not attempt to u= se > 16? And what happens if it does? PF is programming the VF msix capability in the device. So virtio pci drive= r operating the PCI VF device cannot access vectors beyond the max value pr= ogrammed by the PF driver. > Again, something to address. Yes, this has to be described in the spec text. Will add more clearly in v2= . >=20 >=20 > -- > MST