Messages in this thread | | | From | "Liu, Yi L" <> | Subject | RE: [PATCH v4 07/12] iommufd: Add data structure for Intel VT-d stage-1 cache invalidation | Date | Fri, 4 Aug 2023 13:04:57 +0000 |
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> From: Tian, Kevin <kevin.tian@intel.com> > Sent: Thursday, August 3, 2023 8:39 AM > > > From: Jason Gunthorpe <jgg@nvidia.com> > > Sent: Wednesday, August 2, 2023 9:48 PM > > > > On Wed, Aug 02, 2023 at 07:41:05AM +0000, Tian, Kevin wrote: > > > > +/** > > > > + * struct iommu_hwpt_vtd_s1_invalidate - Intel VT-d cache invalidation > > > > + * (IOMMU_HWPT_TYPE_VTD_S1) > > > > + * @flags: Must be 0 > > > > + * @entry_size: Size in bytes of each cache invalidation request > > > > + * @entry_nr_uptr: User pointer to the number of invalidation requests. > > > > + * Kernel reads it to get the number of requests and > > > > + * updates the buffer with the number of requests that > > > > + * have been processed successfully. This pointer must > > > > + * point to a __u32 type of memory location. > > > > + * @inv_data_uptr: Pointer to the cache invalidation requests > > > > + * > > > > + * The Intel VT-d specific invalidation data for a set of cache invalidation > > > > + * requests. Kernel loops the requests one-by-one and stops when > > failure > > > > + * is encountered. The number of handled requests is reported to user > > by > > > > + * writing the buffer pointed by @entry_nr_uptr. > > > > + */ > > > > +struct iommu_hwpt_vtd_s1_invalidate { > > > > + __u32 flags; > > > > + __u32 entry_size; > > > > + __aligned_u64 entry_nr_uptr; > > > > + __aligned_u64 inv_data_uptr; > > > > +}; > > > > + > > > > > > I wonder whether this array can be defined directly in the common > > > struct iommu_hwpt_invalidate so there is no need for underlying > > > iommu driver to further deal with user buffers, including various > > > minsz/backward compat. check. > > > > You want to have an array and another chunk of data? > > > > What is the array for? To do batching? > > yes, it's for batching > > > > > It means we have to allocate memory on this path, that doesn't seem > > like the right direction for a performance improvement.. > > It reuses the ucmd_buffer to avoid memory allocation:
I guess your point is to copy each invalidation descriptor in the common layer and pass the descriptor to iommu driver. right?
> @@ -485,6 +485,12 @@ union ucmd_buffer { > #ifdef CONFIG_IOMMUFD_TEST > struct iommu_test_cmd test; > #endif > + /* > + * hwpt_type specific structure used in the cache invalidation > + * path. > + */ > + struct iommu_hwpt_vtd_s1_invalidate vtd; > + struct iommu_hwpt_vtd_s1_invalidate_desc req_vtd; > }; > > I don't quite like this way.
This is because each descriptor is stored in the uncmd_buffer. So Need to put the struct iommu_hwpt_vtd_s1_invalidate_desc here.
> > > > Having the driver copy in a loop might be better > > > > Can you elaborate?
I think Jason means the way in patch 09.
Regards, Yi Liu
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