From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 24A8898642C for ; Mon, 31 Oct 2022 18:52:30 +0000 (UTC) Date: Mon, 31 Oct 2022 13:24:30 -0400 From: Stefan Hajnoczi Message-ID: References: <20221007165643.3920613-1-usama.arif@bytedance.com> <20221007165643.3920613-4-usama.arif@bytedance.com> <20221031114132-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="eWWCR2o7eA8vMDI1" Content-Disposition: inline In-Reply-To: <20221031114132-mutt-send-email-mst@kernel.org> Subject: Re: [virtio-dev] Re: [PATCH v3 3/4] content: Introduce driver/device auxiliary notifications for MMIO To: "Michael S. Tsirkin" Cc: Usama Arif , virtio-dev@lists.oasis-open.org, ndragazis@arrikto.com, fam.zheng@bytedance.com, liangma@liangbit.com List-ID: --eWWCR2o7eA8vMDI1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Oct 31, 2022 at 11:45:55AM -0400, Michael S. Tsirkin wrote: > On Thu, Oct 27, 2022 at 05:27:28PM -0400, Stefan Hajnoczi wrote: > > On Fri, Oct 07, 2022 at 05:56:42PM +0100, Usama Arif wrote: > > > This includes the additions to the corresponding device and driver > > > conformances. > > >=20 > > > Signed-off-by: Usama Arif > > > Signed-off-by: Stefan Hajnoczi > >=20 > > You can keep this. One thought: > >=20 > > I realized that virtio-mmio support won't be very useful until > > virtio-mmio gets MSI-X support because drivers currently cannot > > differentiate between device auxiliary notifications. > >=20 > > Stefan >=20 >=20 > The big issue with MSI is it actually needs a ton of registers > for interrupt rebalancing, masking etc and they need to be fast. > Maybe a status bit like pci has makes sense here. This patch does add an ISR bit: diff --git a/content.tex b/content.tex index 33362b7..8968fcd 100644 --- a/content.tex +++ b/content.tex @@ -2049,6 +2049,8 @@ \subsection{MMIO Device Register Layout}\label{sec:Vi= rtio Transport Options / Vi in at least one of the active virtual queues. \item [Configuration Change Notification] - bit 1 - the interrupt was asserted because the configuration of the device has changed. + \item [Device-specific Driver Auxiliary Notification] - bit 2 - the = interrupt was + asserted because a device-specific event occurred to notify the dr= iver. The problem is that the driver doesn't know which device-specific event occurred, so the mechanism is less useful than the MSI-X approach where the driver knows exactly which (of potentially many) device-specific events occurred. Stefan --eWWCR2o7eA8vMDI1 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmNgBM4ACgkQnKSrs4Gr c8jpGAgAyd2EBROR2lev/yVmHtwLlEA140mnnRhco7+RCPsla0o2XX4upfdjH2eW oqR+ocq0TLzAinXBPfZBfTfe9s/LDyvVQfuksXgP7tHsSitQD7eAMRvihNNxpZvW DNsL5FgdEZHv5KGn6NtFkrYhllPEofO1wF4aGZ01dZi4/XV/W3Y/8e4LBe4DFyPU +5L9en4oq6OI+TSAR2Z65YtCCuW9GSvj4HtuqLw5MSqJKRoc9IHX4HPptKfKvSTJ dQciED1dJWydzmHfHRQhgkNrkEKtUBm5MIYSzf+6bJQ+5VpGEmYIM6pmvnvO2MHH 63c2B9JeCC70rM5rLImHeVuSA7p5jQ== =pjtm -----END PGP SIGNATURE----- --eWWCR2o7eA8vMDI1--