From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-return-3415-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Date: Wed, 27 Nov 2019 16:17:29 -0500 From: "Michael S. Tsirkin" Message-ID: <20191127161428-mutt-send-email-mst@kernel.org> References: <20191028105508.31769-1-mst@redhat.com> MIME-Version: 1.0 In-Reply-To: Subject: [virtio] Re: [virtio-comment] [PATCH] content: add vendor specific cfg type Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline To: Christophe de Dinechin Cc: virtio@lists.oasis-open.org, virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org List-ID: On Wed, Nov 27, 2019 at 03:54:17PM +0100, Christophe de Dinechin wrote: >=20 >=20 > > On 28 Oct 2019, at 11:55, Michael S. Tsirkin wrote: > >=20 > > Vendors might want to add their own capability > > in the PCI capability list. However, Virtio already > > uses the vendor specific capability ID (0x09) > > for its own purposes. > >=20 > > Provide a structure for vendor specific extensions. > >=20 > > Signed-off-by: Michael S. Tsirkin > > --- > > content.tex | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 80 insertions(+) > >=20 > > diff --git a/content.tex b/content.tex > > index b1ea9b9..8a79b03 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -691,6 +691,8 @@ \subsection{Virtio Structure PCI Capabilities}\labe= l{sec:Virtio Transport Option > > #define VIRTIO_PCI_CAP_PCI_CFG 5 > > /* Shared memory region */ > > #define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8 > > +/* Vendor-specific data */ > > +#define VIRTIO_PCI_CAP_VENDOR_CFG 9 > > \end{lstlisting} > >=20 > > Any other value is reserved for future use. > > @@ -1099,6 +1101,84 @@ \subsubsection{Shared memory capability}\label{s= ec:Virtio Transport Options / Vi > >=20 > > The \field{cap.id} MUST be unique for any one device instance. > >=20 > > +\devicenormative{\paragraph}{Device-specific configuration}{Virtio Tra= nsport Options / Virtio Over PCI Bus / PCI Device Layout / Shared memory ca= pability} > > + > > +The region defined by the combination of the \field {cap.offset}, > > +\field {cap.offset_hi}, and \field {cap.length}, \field > > +{cap.length_hi} fields MUST be contained within the declared bar. >=20 > Uppercase BAR? \field{bar} I think. But really this is from "shared memory: Define PCI capability" that I somehow failed to apply properly :( > > + > > +The \field{cap.id} MUST be unique for any one device instance. > > + > > +\subsubsection{Vendor data capability}\label{sec:Virtio > > +Transport Options / Virtio Over PCI Bus / PCI Device Layout / > > +Vendor data capability} > > + > > +The optional Vendor data capability allows the device to present > > +vendor-specific data to the driver, without > > +conflicts, for debugging and/or reporting purposes, > > +and without conflicting with standard functionality. > > + > > +This capability augments but does not replace the standard > > +subsystem ID and subsystem vendor ID fields > > +(offsets 0x2C and 0x2E in the PCI configuration space header) > > +as specified by \hyperref[intro:PCI]{[PCI]}. > > + > > +Vendor data capability is enumerated on the PCI transport > > +as a VIRTIO_PCI_CAP_VENDOR_CFG capability. > > + > > +The capability has the following structure: > > +\begin{lstlisting} > > +struct virtio_pci_vndr_data { > > + u8 cap_vndr; /* Generic PCI field: PCI_CAP_ID_VNDR */ > > + u8 cap_next; /* Generic PCI field: next ptr. */ > > + u8 cap_len; /* Generic PCI field: capability length */ > > + u8 cfg_type; /* Identifies the structure. */ > > + u16 vendor_id; /* Identifies the vendor-specific format. */ > > +=09/* For Vendor Definition */ > > +=09/* Pads structure to a multiple of 4 bytes */ > > +=09/* Reads must not have side effects */ > > +}; > > +\end{lstlisting} > > + > > +Where \field{vendor_id} identifies the PCI-SIG assigned Vendor ID > > +as specified by \hyperref[intro:PCI]{[PCI]}. > > + > > +Note that the capability size is required to be a multiple of 4. > > + > > +To make it safe for a generic driver to access the capability, > > +reads from this capability MUST NOT have any side effects. >=20 > I think the intent is that this includes the capability payload, not > just the generic fields. Worth spelling out? >=20 > > + > > +\devicenormative{\subsection}{Vendor data capability}{Virtio > > +Transport Options / Virtio Over PCI Bus / PCI Device Layout / > > +Vendor data capability} > > + > > +The device SHOULD present the PCI subsystem vendor ID matching > > +the device vendor, at offset 0x2C in its PCI configuration space > > +header. > > + > > +Devices CAN present \field{vendor_id} that does not match > > +either the PCI Vendor ID or the PCI Subsystem Vendor ID. > > + > > +Devices CAN present multiple Vendor data capabilities with > > +either different or identical \field{vendor_id} values. > > + > > +The value \field{vendor_id} MUST NOT equal 0x1AF4. > > + > > +The size of the Vendor data capability MUST be a multiple of 4 bytes. > > + > > +Reads of the Vendor data capability by the driver MUST NOT have any > > +side effects. > > + > > +\drivernormative{\subsection}{Vendor data capability}{Virtio > > +Transport Options / Virtio Over PCI Bus / PCI Device Layout / > > +Vendor data capability} > > + > > +The driver SHOULD NOT use the Vendor data capability except > > +for debugging and reporting purposes. >=20 > What is the rationale for this restriction? >=20 > For example, would it be OK for a vendor to expose the presence > of a particular firmware bugfix, so that the driver could disable > some bug workaround? You seem to hint that this is the intent > in a later response, but on initial reading, it was not clear to me > that such usage would fit under =E2=80=9Cdebugging=E2=80=9D or =E2=80=9Cr= eporting=E2=80=9D. >=20 > (I=E2=80=99m quite new here, so feel free to ignore if it=E2=80=99s clear= to everybody else) >=20 >=20 > > + > > +The driver MUST qualify the \field{vendor_id} before > > +interpreting or writing into the Vendor data capability. > > + > > \subsubsection{PCI configuration access capability}\label{sec:Virtio Tr= ansport Options / Virtio Over PCI Bus / PCI Device Layout / PCI configurati= on access capability} > >=20 > > The VIRTIO_PCI_CAP_PCI_CFG capability > > --=20 > > MST > >=20 > >=20 > > This publicly archived list offers a means to provide input to the > > OASIS Virtual I/O Device (VIRTIO) TC. > >=20 > > In order to verify user consent to the Feedback License terms and > > to minimize spam in the list archive, subscription is required > > before posting. > >=20 > > 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.p= df > > 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/ > >=20 --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that=20 generates this mail. 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