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Subject: RE: [PATCH v10 4/4] transport-pci: Introduce group legacy group member config region access
> 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 the any of the notification region at offset 0 supplied by the device in 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.
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