Commit ed739b8f authored Feb 22, 2024 by Jason Gunthorpe Committed by Jason Zeng Feb 25, 2024

iommu/sva: Restore SVA handle sharing

mainline inclusion
from mainline-v6.8-rc6
commit 65d4418c5002ec5b0e529455bf4152fd43459079
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I938E2
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=65d4418c5002ec5b0e529455bf4152fd43459079



--------------------------------

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>

parent 5f7e9475

drivers/iommu/iommu-sva.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -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);

include/linux/iommu.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -1010,11 +1010,14 @@ struct iommu_fwspec {
		struct iommu_sva {
		struct device *dev;
		struct iommu_domain *domain;
		struct list_head handle_item;
		refcount_t users;
		};

		struct iommu_mm_data {
		u32 pasid;
		struct list_head sva_domains;
		struct list_head sva_handles;
		};

		int iommu_fwspec_init(struct device dev, struct fwnode_handle iommu_fwnode,