From 65d4418c5002ec5b0e529455bf4152fd43459079 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Thu, 22 Feb 2024 10:07:41 -0400 Subject: 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 Closes: https://lore.kernel.org/all/20240221110658.529-1-zhangfei.gao@linaro.org/ Tested-by: Zhangfei Gao Signed-off-by: Jason Gunthorpe Reviewed-by: Lu Baolu Link: https://lore.kernel.org/r/0-v1-9455fc497a6f+3b4-iommu_sva_sharing_jgg@nvidia.com Signed-off-by: Joerg Roedel --- include/linux/iommu.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include') diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 1ea2a820e1eb..5e27cb3a3be9 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -892,11 +892,14 @@ 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, -- cgit v1.2.3