On Thu, May 15, 2025 at 05:58:41AM +0000, Tian, Kevin wrote:
From: Nicolin Chen nicolinc@nvidia.com Sent: Friday, May 9, 2025 11:03 AM
Add IOMMUFD_OBJ_HW_QUEUE with an iommufd_hw_queue structure, representing a HW-accelerated queue type of IOMMU's physical queue that can be passed through to a user space VM for direct hardware control, such as:
- NVIDIA's Virtual Command Queue
- AMD vIOMMU's Command Buffer, Event Log Buffer, and PPR Log Buffer
Introduce an allocator iommufd_hw_queue_alloc(). And add a pair of viommu ops for iommufd to forward user space ioctls to IOMMU drivers.
Given that the first user of this HW QUEUE (tegra241-cmdqv) will need to ensure the queue memory to be physically contiguous, add a flag property in iommufd_viommu_ops and IOMMUFD_VIOMMU_FLAG_HW_QUEUE_READS_PA to allow driver to flag it so that the core will validate the physical pages of a given guest queue.
'READS' is confusing here. What about xxx_CONTIG_PAS?
Combining Jason's first comments here: https://lore.kernel.org/linux-iommu/20250515160620.GJ382960@nvidia.com/
So, pinning should be optional too. And I think there would be unlikely a case where HW needs contiguous physical pages while not requiring to pin the pages, right?
So, we need an flag that could indicate to do both tests. Yet, "xxx_CONTIG_PAS" doesn't sound very fitting, compared to this "IOMMUFD_VIOMMU_FLAG_HW_QUEUE_READS_PA".
Perhaps, we should just add some comments to clarify a bit. Or do you have some better naming?
Thanks Nicolin