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Subject: Re: [PATCH v2 4/4] Add CCW configuration field "indirect_num" to vq_info_block
On Donnerstag, 10. März 2022 16:26:46 CET Stefan Hajnoczi wrote: > On Mon, Feb 21, 2022 at 06:01:41PM +0100, Christian Schoenebeck wrote: > > This new CCW configuration field allows to negotiate a more fine > > graded maximum lenght of indirect descriptor chains. > > > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/122 > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> I'll fix those accidentally added double SOBs BTW. > > --- > > > > content.tex | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/content.tex b/content.tex > > index a3baf4d..d400ea7 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -2599,6 +2599,7 @@ \subsubsection{Configuring a > > Virtqueue}\label{sec:Virtio Transport Options / Vir> > > be16 num; > > be64 driver; > > be64 device; > > > > + be32 indirect_num; > > > > }; > > \end{lstlisting} > > > > @@ -2607,6 +2608,10 @@ \subsubsection{Configuring a > > Virtqueue}\label{sec:Virtio Transport Options / Vir> > > available area and used area for queue \field{index}, respectively. The > > actual virtqueue size (number of allocated buffers) is transmitted in > > \field{num}.> > > +If VIRTIO_RING_F_INDIRECT_SIZE has been negotiated then > > \field{indirect_num} +reflects the maximum length of indirect descriptor > > tables for queue +\field{index}. > > I think the transfer direction of CCW_CMD_SET_VQ struct vq_info_block is > driver-to-device. So it allows the driver to set the Queue Indirect > Size, but how does the driver query the device's maximum Queue Indirect > Size value? Ah, seems you are right Stefan. I assumed this was similar to PCI. So the way to go on CCW would be an additional (equally named?) field in struct vq_info_block (CCW_CMD_READ_VQ_CONF) for device -> driver? Cornelia? Best regards, Christian Schoenebeck
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