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 <> > ---
> 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 > > >
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