On Fri, Dec 15, 2023 at 01:50:07AM +0000, Tian, Kevin wrote:
From: Liu, Yi L yi.l.liu@intel.com Sent: Thursday, December 14, 2023 7:27 PM
On 2023/11/17 21:18, Yi Liu wrote:> This adds the data structure for flushing iotlb for the nested domain
+struct iommu_hwpt_vtd_s1_invalidate {
__aligned_u64 addr;__aligned_u64 npages;__u32 flags;__u32 __reserved;__u32 error;__u32 dev_id;+};
dev_id is used to report the failed device, userspace should be able to map it to a vRID, and inject it to VM as part of ITE/ICE error.
However, I got a problem when trying to get dev_id in cache invalidation path, since this is filled in intel iommu driver. Seems like there is no good way for it. I've below alternatives to move forward, wish you have a look.
- Reuse Nicolin's vRID->pRID mapping. If thevRID->pRID mapping is
maintained, then intel iommu can report a vRID back to user. But intel iommu driver does not have viommu context, no place to hold the vRID-
pRID
mapping. TBH. It may require other reasons to introduce it other than the error reporting need. Anyhow, this requires more thinking and also has dependency even if it is doable in intel side.
this sounds like a cleaner way to inject knowledge which iommu driver requires to find out the user tag. but yes it's a bit weird to introduce viommu awareness in intel iommu driver when there is no such thing in real hardware.
I think a viommu is defined more like a software object representing the virtual IOMMU in a VM. Since VT-d has a vIOMMU in a nesting case, there could be an object for it too?
and for this error reporting case what we actually require is the reverse map i.e. pRID->vRID. Not sure whether we can leverage the same RID mapping uAPI as for ARM/AMD but ignore viommu_id and then store vRID under device_domain_info. a bit tricky on life cycle management and also incompatible with SIOV...
One thing that I am not very clear here: since both vRID and dev_id are given by the VMM, shouldn't it already know the mapping if the point is to translate (pRID->)dev_id->vRID?
Thanks Nicolin