Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE

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On 11/17/23 9:07 PM, Yi Liu wrote:
In nested translation, the stage-1 page table is user-managed but cached
by the IOMMU hardware, so an update on present page table entries in the
stage-1 page table should be followed with a cache invalidation.

Add an IOMMU_HWPT_INVALIDATE ioctl to support such a cache invalidation.
It takes hwpt_id to specify the iommu_domain, and a multi-entry array to
support multiple invalidation requests in one ioctl.

Check cache_invalidate_user op in the iommufd_hw_pagetable_alloc_nested,
since all nested domains need that.

Co-developed-by: Nicolin Chen<nicolinc@xxxxxxxxxx>
Signed-off-by: Nicolin Chen<nicolinc@xxxxxxxxxx>
Signed-off-by: Yi Liu<yi.l.liu@xxxxxxxxx>
---
  drivers/iommu/iommufd/hw_pagetable.c    | 35 +++++++++++++++++++++++++
  drivers/iommu/iommufd/iommufd_private.h |  9 +++++++
  drivers/iommu/iommufd/main.c            |  3 +++
  include/uapi/linux/iommufd.h            | 35 +++++++++++++++++++++++++
  4 files changed, 82 insertions(+)

diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index 2abbeafdbd22..367459d92f69 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -238,6 +238,11 @@ iommufd_hwpt_nested_alloc(struct iommufd_ctx *ictx,
  		rc = -EINVAL;
  		goto out_abort;
  	}
+	/* Driver is buggy by missing cache_invalidate_user in domain_ops */
+	if (WARN_ON_ONCE(!hwpt->domain->ops->cache_invalidate_user)) {
+		rc = -EINVAL;
+		goto out_abort;
+	}
  	return hwpt_nested;

The WARN message here may cause kernel regression when users bisect
issues. Till this patch, there are no drivers support the
cache_invalidation_user callback yet.

Best regards,
baolu




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