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Subject: Re: [virtio-comment] Re: [virtio-dev] [PATCH v4 2/3] shared memory: Define PCI capability
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" <dgilbert@redhat.com> > > > > Define the PCI capability used for enumerating shared memory regions. > > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > > Reviewed-by: Cornelia Huck <cohuck@redhat.com> > > --- > > 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? > > > + > > +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/
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