[virtio-dev] Re: [PATCH v10 4/4] transport-pci: Introduce group legacy group member config region access

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jul 06, 2023 at 06:16:10PM +0000, Parav Pandit wrote:
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Thursday, July 6, 2023 2:06 PM
> > 
> > But again even if you add it there, you can not claim it's exactly the same as
> > legacy because the address is different, the address type is different, the driver
> > is different (this is owner driver) and even the device is different.
> > 
> You drafted below, that I included,
> 
> The driver of the owner device can send a driver notification to the member
> device by executing VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE with the
> \field{offset} matching \field{Queue Notify} and the \field{data} containing
> the virtqueue index to be notified.
> 
> We extend this further by saying Queue notify notifications is sent via MMIO as,
> 
> The driver of the owner device can send a driver notification to the member
> device by executing VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE with the
> \field{offset} matching \field{Queue Notify} and the \field{data} containing
> the virtqueue index to be notified or by performing memory or I/O write in

split to two sentences please. E.g.
Alternatively, the driver ...

> the any of the notification region at offset 0 supplied by the device in 

the any is agrammatical

> VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO result.
> 
> > Please also call out the unusual configuration where the type is "member" and
> > then you have the owner driver access the memory of the member device.
> > People might be confused.
> > 
> > I also think we should explain that order of entries is a hint to driver: use the 1st
> > entry that you can.
> 
> Driver really can choose any valid entry out of the 4 that driver likes.
> I really don't see a need for overwriting this area as I fail to see why one will expose multiple entries from the device side in reality.

I do: one for owner one for member.
which is best for device is device specific.

I don't know what do you mean by "overwriting". Explaining in detail?
You feel like this because you spent a lot of time thinking
about the area and there is a specific solution is very clear in your head.
First readers are not like this and second they might have a
different solution.

-- 
MST


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