Re: [PATCH v3 3/8] iommufd: Add fault and response message definitions

From: Baolu Lu
Date: Mon Mar 25 2024 - 08:44:45 EST


On 3/23/24 1:04 AM, Jason Gunthorpe wrote:
+struct iommu_hwpt_pgfault {
+ __u32 size;
+ __u32 flags;
+ __u32 dev_id;
+ __u32 pasid;
+ __u32 grpid;
+ __u32 perm;
+ __u64 addr;
+};
Do we need an addr + size here? I've seen a few things where I wonder
if that might become an enhancment someday.
I am not sure. The page size is not part of ATS/PRI. Can you please
elaborate a bit about how the size could be used? Perhaps I
misunderstood here?
size would be an advice how much data the requestor is expecting to
fetch. Eg of the PRI initiator knows it is going to do a 10MB transfer
it could fill in 10MB and the OS could pre-fault in 10MB of IOVA.

It is not in the spec, it may never be in the spec, but it seems like
it would be good to consider it, at least make sure we have
compatability to add it later.

Thanks for the explanation. It sounds reasonable. I will take it and add
some comments to explain the motivation as you described above.

Best regards,
baolu