Hi Nicolin, Jason,


On 5/8/2025 10:42 PM, Nicolin Chen wrote:

On Thu, May 08, 2025 at 09:14:56AM -0300, Jason Gunthorpe wrote:

quoted

On Wed, May 07, 2025 at 10:56:17PM -0700, Nicolin Chen wrote:

quoted

What I am not sure is if the HW allows setting the ComWaitIntEn bit
after CmdBufEn=1, which seems to be unlikely but the spec does not
highlight. If so, this would be an modification to the HW QUEUE, in
which case we could either do an relocation of the HW QUEUE (where
we can set the flag in the 2nd allocation) or add an new option via
IOMMUFD_CMD_OPTION (as Kevin suggested), and I think it should be
a per-HW_QUEUE option since it doesn't affect other type of queues
like Event/PRR Log Buffers.

The main question is if the control is global to the entire VIOMMU and
all its HW QUEUE's or local to a single HW QUEUE.

Oh, that's right.. I recall AMD only has one Command Buffer,
but can have dual Event Log Buffers and dual PPR Log Buffers.

Right.

And the EventIntEn or PprIntEn bit seem to be global for the
dual buffers..

Yes. But there are other bit to configure dual buffers etc.
(like DualEventLogEn).

quoted

If it is global then some "modify viommu" operation should be used to
change it.

If it is local then some "modify hw queu" operation.

IOMMUFD_CMD_OPTION could be used with an object_id == VIOMMU as a kind
of modify..

Vasant can confirm. But looks like it should be a vIOMMU
option.

I think CMD_OPTION will work. So something like below?

if (cmd_option_id == IOMMU_OPTION_VIOMMU && cmd->object_id == viommu_id)
	iommufd_viommu->ops->viommu_options() ?


-Vasant