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authorJason Gunthorpe <jgg@nvidia.com>2024-02-22 10:07:41 -0400
committerJoerg Roedel <jroedel@suse.de>2024-02-23 16:45:05 +0100
commit65d4418c5002ec5b0e529455bf4152fd43459079 (patch)
tree5e9cdeb9b970da41c8901b8f4bd1320f10e7f0e9 /drivers
parent16b1b39126e5d5d49eedb2245f9e781b22bde926 (diff)
iommu/sva: Restore SVA handle sharing
Prior to commit 092edaddb660 ("iommu: Support mm PASID 1:n with sva domains") the code allowed a SVA handle to be bound multiple times to the same (mm, device) pair. This was alluded to in the kdoc comment, but we had understood this to be more a remark about allowing multiple devices, not a literal same-driver re-opening the same SVA. It turns out uacce and idxd were both relying on the core code to handle reference counting for same-device same-mm scenarios. As this looks hard to resolve in the drivers bring it back to the core code. The new design has changed the meaning of the domain->users refcount to refer to the number of devices that are sharing that domain for the same mm. This is part of the design to lift the SVA domain de-duplication out of the drivers. Return the old behavior by explicitly de-duplicating the struct iommu_sva handle. The same (mm, device) will return the same handle pointer and the core code will handle tracking this. The last unbind of the handle will destroy it. Fixes: 092edaddb660 ("iommu: Support mm PASID 1:n with sva domains") Reported-by: Zhangfei Gao <zhangfei.gao@linaro.org> Closes: https://lore.kernel.org/all/20240221110658.529-1-zhangfei.gao@linaro.org/ Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Link: https://lore.kernel.org/r/0-v1-9455fc497a6f+3b4-iommu_sva_sharing_jgg@nvidia.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/iommu/iommu-sva.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index c3fc9201d0be..7f91c8d0064b 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -41,6 +41,7 @@ static struct iommu_mm_data *iommu_alloc_mm_data(struct mm_struct *mm, struct de
}
iommu_mm->pasid = pasid;
INIT_LIST_HEAD(&iommu_mm->sva_domains);
+ INIT_LIST_HEAD(&iommu_mm->sva_handles);
/*
* Make sure the write to mm->iommu_mm is not reordered in front of
* initialization to iommu_mm fields. If it does, readers may see a
@@ -82,6 +83,14 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
goto out_unlock;
}
+ list_for_each_entry(handle, &mm->iommu_mm->sva_handles, handle_item) {
+ if (handle->dev == dev) {
+ refcount_inc(&handle->users);
+ mutex_unlock(&iommu_sva_lock);
+ return handle;
+ }
+ }
+
handle = kzalloc(sizeof(*handle), GFP_KERNEL);
if (!handle) {
ret = -ENOMEM;
@@ -108,7 +117,9 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
if (ret)
goto out_free_domain;
domain->users = 1;
+ refcount_set(&handle->users, 1);
list_add(&domain->next, &mm->iommu_mm->sva_domains);
+ list_add(&handle->handle_item, &mm->iommu_mm->sva_handles);
out:
mutex_unlock(&iommu_sva_lock);
@@ -141,6 +152,12 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
struct device *dev = handle->dev;
mutex_lock(&iommu_sva_lock);
+ if (!refcount_dec_and_test(&handle->users)) {
+ mutex_unlock(&iommu_sva_lock);
+ return;
+ }
+ list_del(&handle->handle_item);
+
iommu_detach_device_pasid(domain, dev, iommu_mm->pasid);
if (--domain->users == 0) {
list_del(&domain->next);