RE: [PATCH v3 11/23] iommufd/viommu: Add IOMMUFD_CMD_VQUEUE_ALLOC ioctl

From: Vasant Hegde vasant.hegde@amd.com Sent: Wednesday, May 7, 2025 3:42 PM

Hi Jason,

On 5/6/2025 5:31 PM, Jason Gunthorpe wrote:

...

Do you need a modify queue operation?

We have two types of operations. One that impacts the queue, other set of bits which doesn't operate on qeueue.

ex: Event log buffer

• We configure "MMIO Offset 0010h Event Log Base Address Register" with

Base address and size

• MMIO Offset 0018h IOMMU Control Register EventLogEn: Event log enable

  • When guest sets this bit, qemu will trap and will send queue_alloc
  • When guest disables this bit, qemu will trap and send vqueue_destroy

  This part is fine.

  EventIntEn: Event log interrupt enable

  • When guest sets this bit, qemu will trap
  • this needs to be communicated to Host so that we can program VF

Control BAR and enable the interrupt

• There is other bit "Completion wait interrupt enable" This doesn't related to any buffer. Instead if we configure this for

completion wait command it will generate interrupt.

I am asking how do we handle above two steps? Should it be part of queue IOCTL or may be some other IOCTL which just passes these info to HW driver?

Probably IOMMUFD_CMD_OPTION can server the purpose?