From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-756-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id BAA63985DBB for ; Thu, 20 Jun 2019 05:45:11 +0000 (UTC) Date: Thu, 20 Jun 2019 01:45:07 -0400 From: "Michael S. Tsirkin" Message-ID: <20190620014413-mutt-send-email-mst@kernel.org> References: <20190320120740.8514-1-dgilbert@redhat.com> <20190320120740.8514-3-dgilbert@redhat.com> <20190617143100-mutt-send-email-mst@kernel.org> <20190617144014-mutt-send-email-mst@kernel.org> <20190619171316.GF2844@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190619171316.GF2844@work-vm> Subject: Re: [virtio-comment] Re: [virtio-dev] [PATCH v4 2/3] shared memory: Define PCI capability To: "Dr. David Alan Gilbert" Cc: virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org, stefanha@redha.com, cohuck@redhat.com List-ID: On Wed, Jun 19, 2019 at 06:13:17PM +0100, Dr. David Alan Gilbert wrote: > * Michael S. Tsirkin (mst@redhat.com) wrote: > > On Mon, Jun 17, 2019 at 02:36:43PM -0400, Michael S. Tsirkin wrote: > > > On Wed, Mar 20, 2019 at 12:07:39PM +0000, Dr. David Alan Gilbert (git) wrote: > > > > From: "Dr. David Alan Gilbert" > > > > > > > > Define the PCI capability used for enumerating shared memory regions. > > > > > > > > Signed-off-by: Dr. David Alan Gilbert > > > > Reviewed-by: Stefan Hajnoczi > > > > Reviewed-by: Cornelia Huck > > > > --- > > > > content.tex | 37 +++++++++++++++++++++++++++++++++++++ > > > > 1 file changed, 37 insertions(+) > > > > > > > > diff --git a/content.tex b/content.tex > > > > index 8cd1a38..ddbf949 100644 > > > > --- a/content.tex > > > > +++ b/content.tex > > > > @@ -688,6 +688,8 @@ The fields are interpreted as follows: > > > > #define VIRTIO_PCI_CAP_DEVICE_CFG 4 > > > > /* PCI configuration access */ > > > > #define VIRTIO_PCI_CAP_PCI_CFG 5 > > > > +/* Shared memory region */ > > > > +#define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8 > > > > \end{lstlisting} > > > > > > > > Any other value is reserved for future use. > > > > @@ -1052,6 +1054,41 @@ any device type which has a device-specific configuration. > > > > > > > > The \field{offset} for the device-specific configuration MUST be 4-byte aligned. > > > > > > > > +\subsubsection{Shared memory capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory capability} > > > > + > > > > +Shared memory regions \ref{sec:Basic Facilities of a Virtio > > > > +Device / Shared Memory Regions} are enumerated on the PCI transport > > > > +as a sequence of VIRTIO_PCI_CAP_SHARED_MEMORY_CFG capabilities, one per region. > > > > + > > > > +The capability is immediately followed by an additional field like so: > > > > + > > > > +\begin{lstlisting} > > > > +struct virtio_pci_shm_cap { > > > > + struct virtio_pci_cap cap; > > > > + u32 offset_hi; > > > > + u32 length_hi; > > > > + u8 id; > > > > > > Pls pad, pci capabilities must be a multiple of 4 bytes. > > > BTW virtio_pci_cap has 3 bytes of padding. > > > We can stick the id there maybe? > > > > > > > +}; > > > > +\end{lstlisting} > > > > + > > > > +Given that the \field{cap.length} and \field{cap.offset} fields > > > > +are only 32 bit, the additional \field{offset_hi} and \field {length_hi} > > > > +fields provide the most significant 32 bits of a total 64 bit offset and > > > > +length within the bar specified by \field{cap.bar}. \field{id} > > > > +uniquely identifies the given shared memory region using a device > > > > +specific identifier. > > > > > > I didn't realize we will ever need so much space. I think I prefer > > > moving offset_hi/length_hi to a general virtio_pci_cap64 that others can > > > reuse. > > > > And maybe we should set a bit in some other reserved byte > > so people can generally use 64 bit offsets/lengths? > > Is it actually any cleaner? I don't know - where would you put that bit? > > Dave We'd put it either in bar or cfg type. No, I'm not sure it's strictly required. It saves a bit of config space but increases complexity for guests .... > > > > > > > + > > > > +While most capabilities can not be repeated, > > > > > > I'd drop this part. > > > > > > > multiple > > > > +VIRTIO_PCI_CAP_SHARED_MEMORY_CFG capabilities are allowed as long > > > > +as the \field{id} is unique. > > > > + > > > > +\devicenormative{\paragraph}{Device-specific configuration}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory capability} > > > > + > > > > +The region defined by the combination of the offsets and length > > > > +fields > > > > > > let's do \field{cap.length} \field{cap.offset} etc. > > > > > > >MUST be contained within the declared bar. > > > > + > > > > +The \field{id} MUST be unique for any one device instance. > > > > + > > > > \subsubsection{PCI configuration access capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / PCI configuration access capability} > > > > > > > > The VIRTIO_PCI_CAP_PCI_CFG capability > > > > -- > > > > 2.20.1 > > > > > > > > > > > > --------------------------------------------------------------------- > > > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > > > > > > This publicly archived list offers a means to provide input to the > > > OASIS Virtual I/O Device (VIRTIO) TC. > > > > > > In order to verify user consent to the Feedback License terms and > > > to minimize spam in the list archive, subscription is required > > > before posting. > > > > > > Subscribe: virtio-comment-subscribe@lists.oasis-open.org > > > Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org > > > List help: virtio-comment-help@lists.oasis-open.org > > > List archive: https://lists.oasis-open.org/archives/virtio-comment/ > > > Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf > > > List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists > > > Committee: https://www.oasis-open.org/committees/virtio/ > > > Join OASIS: https://www.oasis-open.org/join/ > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. 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