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| author | Nicolin Chen <nicolinc@nvidia.com> | 2023-10-23 18:29:58 -0700 |
|---|---|---|
| committer | Jason Gunthorpe <jgg@nvidia.com> | 2023-10-24 12:56:37 -0300 |
| commit | 2ccabf81ddff81355bf044bdad3c44e9e6ac32d9 (patch) | |
| tree | d8a4a81488d15704280614ff7826a1090dcc4cc3 /drivers/iommu/iommufd/hw_pagetable.c | |
| parent | 0795b305da8902e7d092f90bf9a1a2c98f34b1db (diff) | |
| download | lwn-2ccabf81ddff81355bf044bdad3c44e9e6ac32d9.tar.gz lwn-2ccabf81ddff81355bf044bdad3c44e9e6ac32d9.zip | |
iommufd: Only enforce cache coherency in iommufd_hw_pagetable_alloc
According to the conversation in the following link:
https://lore.kernel.org/linux-iommu/20231020135501.GG3952@nvidia.com/
The enforce_cache_coherency should be set/enforced in the hwpt allocation
routine. The iommu driver in its attach_dev() op should decide whether to
reject or not a device that doesn't match with the configuration of cache
coherency. Drop the enforce_cache_coherency piece in the attach/replace()
and move the remaining "num_devices" piece closer to the refcount that is
using it.
Accordingly drop its function prototype in the header and mark it static.
Also add some extra comments to clarify the expected behaviors.
Link: https://lore.kernel.org/r/20231024012958.30842-1-nicolinc@nvidia.com
Suggested-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Diffstat (limited to 'drivers/iommu/iommufd/hw_pagetable.c')
| -rw-r--r-- | drivers/iommu/iommufd/hw_pagetable.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c index 72a5269984b0..c2b742ffeb0c 100644 --- a/drivers/iommu/iommufd/hw_pagetable.c +++ b/drivers/iommu/iommufd/hw_pagetable.c @@ -42,7 +42,7 @@ void iommufd_hw_pagetable_abort(struct iommufd_object *obj) iommufd_hw_pagetable_destroy(obj); } -int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt) +static int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt) { if (hwpt->enforce_cache_coherency) return 0; @@ -116,6 +116,13 @@ iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas, * doing any maps. It is an iommu driver bug to report * IOMMU_CAP_ENFORCE_CACHE_COHERENCY but fail enforce_cache_coherency on * a new domain. + * + * The cache coherency mode must be configured here and unchanged later. + * Note that a HWPT (non-CC) created for a device (non-CC) can be later + * reused by another device (either non-CC or CC). However, A HWPT (CC) + * created for a device (CC) cannot be reused by another device (non-CC) + * but only devices (CC). Instead user space in this case would need to + * allocate a separate HWPT (non-CC). */ if (idev->enforce_cache_coherency) { rc = iommufd_hw_pagetable_enforce_cc(hwpt); |