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Subject: Re: [virtio-comment] [PATCH 1/3] shared memory: Define shared memory regions
* Cornelia Huck (cohuck@redhat.com) wrote: > On Wed, 16 Jan 2019 20:06:25 +0000 > "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote: > > > So these are all moving this 1/3 forward - has anyone got comments on > > the transport specific implementations? > > No comment on pci or mmio, but I've hacked something together for ccw. > Basically, one sense-type ccw for discovery and a control-type ccw for > activation of the regions (no idea if we really need the latter), both > available with ccw revision 3. > > No idea whether this will work this way, though... That sounds (from a shm perspective) reasonable; can I ask why the 'activate' is needed? Dave > diff --git a/content.tex b/content.tex > index 836ee5236939..7f379bca932e 100644 > --- a/content.tex > +++ b/content.tex > @@ -2078,6 +2078,8 @@ virtio: > #define CCW_CMD_READ_VQ_CONF 0x32 > #define CCW_CMD_SET_VIRTIO_REV 0x83 > #define CCW_CMD_READ_STATUS 0x72 > +#define CCW_CMD_GET_REGIONS 0x14 > +#define CCW_CMD_MAP_REGIONS 0x93 > \end{lstlisting} > > \subsubsection{Notifications}\label{sec:Virtio Transport Options / Virtio > @@ -2170,7 +2172,9 @@ The following values are supported: > \hline > 2 & 0 & <empty> & CCW_CMD_READ_STATUS support \\ > \hline > -3-n & & & reserved for later revisions \\ > +3 & 0 & <empty> & CCW_CMD_GET_REGIONS and CCW_CMD_MAP_REGIONS support \\ > +\hline > +4-n & & & reserved for later revisions \\ > \hline > \end{tabular} > > @@ -2449,6 +2453,72 @@ command. Some legacy devices will support two-stage queue indicators, though, > and a driver will be able to successfully use CCW_CMD_SET_IND_ADAPTER to set > them up. > > +\subsubsection{Handling Shared Memory Regions}\label{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Handling Shared Memory Regions} > + > +The CCW_CMD_GET_REGIONS command allows the driver to discover shared memory > +regions provided by the device, if any. > + > +The driver provides a pointer to a 4096 byte buffer that is filled out by > +the device: > + > +\begin{lstlisting} > + struct shared_regions_info { > + be64 num_regions; > + struct shared_region_desc regions[]; > + }; > +\end{lstlisting} > + > +The buffer contains 0 or more shared region descriptors, as specified > +by \field{num_regions}. If the devices does not provide shared regions, > +\field{num_regions} is 0. Otherwise, the shared region descriptors have > +the following format: > + > +\begin{lstlisting} > +struct shared_region_desc { > + be64 addr; > + be64 len; > + u8 id; > + u8 pad[3]; > +} > +\end{lstlisting} > + > +\field{addr} is the guest-physical address of the region with a length of > +\field{len}, identified by \field{id}. The contents of \field{pad} are > +unpredictable, although it is recommended that the device fills in zeroes. > + > +To activate or deactivate a shared memory region, the device uses the > +CCW_CMD_MAP_REGIONS command. It takes the following payload: > + > +\begin{lstlisting} > +struct shared_region_ctrl { > + u8 id; > + u8 activate; > + u8 pad[2]; > +} > +\end{lstlisting} > + > +\field{id} denotes the shared memory region that is the target of the command, > +while \field{activate} specifies whether the region should be activated (if 1) > +or deactivated (if 0). When activated, the device makes the guest-physical > +address of the region available as a shared memory region. > + > +\devicenormative{\paragraph}{Handling Shared Memory Regions}{Virtio Transport Options / Virtio over channel I/O / Device Initialization / Handling Shared Memory Regions} > + > +The device MUST reject the CCW_CMD_GET_REGIONS and CCW_CMD_MAP_REGIONS > +commands if not at least revision 3 has been negotiated. > + > +The device MUST NOT read from or write to the region before it has been > +activated by the driver or after it has been deactivated by the driver. > + > +If the driver reads from or writes to an address specified to a region that is > +not activated by the driver, it MUST treat this read or write as a normal > +read or write operation. > + > +\drivernormative{\paragraph}{Handling Shared Memory Regions}{Virtio Transport Options / Virtio over channel I/O / Device Initialization / Handling Shared Memory Regions} > + > +The driver MUST NOT treat the guest-physical address of a region as a shared > +memory region before it has activated it or after it has deactivated it. > + > \subsection{Device Operation}\label{sec:Virtio Transport Options / Virtio over channel I/O / Device Operation} > > \subsubsection{Host->Guest Notification}\label{sec:Virtio Transport Options / Virtio over channel I/O / Device Operation / Host->Guest Notification} -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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