virtio — archive

[Michael S. Tsirkin <pawel.moll@arm.com>]

On Tue, Aug 05, 2014 at 02:23:55PM +0100, Pawel Moll wrote: > Those changes do not add nor remove any features and constitutes > only error correction and editorial changes. > > * Extra clarifications for QueueReady and ConfigGeneration > * Added alignment requirement section, to formalise > hidden assumptions about register accesses > > Signed-off-by: Pawel Moll <pawel.moll@arm.com> > --- > content.tex 26 ++++++++++++++++++++ ------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/content.tex b/content.tex > index 17ba3b8..9220691 100644 > --- a/content.tex > +++ b/content.tex > @@ -1997,8 +1997,8 @@ All register values are organized as Little Endian. > } > hline > mmioreg{QueueReady}{Virtual queue ready bit}{0x044}{RW}{% > - Writing one (0x1) to this register notifies the device that the > - virtual queue is ready to be used. Reading from this register > + Writing one (0x1) to this register notifies the device that it can > + execute requests from this virtual queue. Reading from this register > returns the last value written to it. Both read and write > accesses apply to the queue selected by writing to field{QueueSel}. > } > @@ -2058,7 +2058,11 @@ All register values are organized as Little Endian. > } > hline > mmioreg{ConfigGeneration}{Configuration atomicity value}{0x0fc}{R}{ > - Changes every time the configuration noticeably changes (see ef {sec:Basic Facilities of a Virtio Device / Device Configuration Space}. > + Reading from this register returns a value describing a version of the device-specific configuration space (see field{Config}). > + The driver can then access the configuration space and, when finished, read field{ConfigGeneration} again. > + If no part of the configuration space has changed between these two field{ConfigGeneration} reads, the returned values are identical. > + If the values are different, the configuration space accesses were not atomic and the driver has to perform the operations again. > + See also ef {sec:Basic Facilities of a Virtio Device / Device Configuration Space}. > } > hline > mmioreg{Config}{Configuration space}{0x100+}{RW}{ > @@ -2083,9 +2087,10 @@ do not represent events which took place MUST be zero. > Upon reset, the device MUST clear all bits in field{InterruptStatus} and ready bits in the > field{QueueReady} register for all queues in the device. > > -The device MUST change field{ConfigGeneration} if there is any risk of a > -device seeing an inconsistent configuration state, but it MAY only change the value > -after a configuration read operation. > +The device MUST change value returned in field{ConfigGeneration} if there is any risk of a > +driver seeing an inconsistent configuration state. > + > +The device MUST NOT access virtual queue contents when field{QueueReady} is zero (0x0). > > drivernormative{subsubsection}{MMIO Device Register Layout}{Virtio Transport Options / Virtio Over MMIO / MMIO Device Register Layout} > The driver MUST NOT access memory locations not described in the > @@ -2094,6 +2099,15 @@ table ef{tab:Virtio Trasport Options / Virtio Over MMIO / MMIO Device Register > MUST NOT write to the read-only registers (direction R) and > MUST NOT read from the write-only registers (direction W). > > +The driver MUST only use 32 bit wide and aligned reads and writes to access the control registers > +described in table ef{tab:Virtio Trasport Options / Virtio Over MMIO / MMIO Device Register Layout}. > +For the device-specific configuration space, the driver MUST use 8 bit wide accesses for > +8 bit wide fields, 16 bit wide and aligned accesses for 16 bit wide fields and 32 bit wide and > +aligned accesses for 32 and 64 bit wide fields. > + > +The driver MAY use other accesses for the device-specific configuration space, > +depending on the device type. > + Could you please clarify what this last phrase means? Do you perhaps mean device MAY accept other accesses? > The driver MUST ignore a device with field{MagicValue} which is not 0x74726976, > although it MAY report an error. > > -- > 1.9.1 > > > --------------------------------------------------------------------- > To unsubscribe from this mail list, you must leave the OASIS TC that > generates this mail. Follow this link to all your TCs in OASIS at: > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php