On 3/8/23 11:02 PM, Jason Gunthorpe wrote:
On Wed, Mar 08, 2023 at 08:32:03PM +0800, Baolu Lu wrote:
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h index 2ff192777f27d3..22863759c3bfb0 100644 --- a/drivers/iommu/iommufd/iommufd_private.h +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -76,10 +76,9 @@ int iopt_table_add_domain(struct io_pagetable *iopt, struct iommu_domain *domain); void iopt_table_remove_domain(struct io_pagetable *iopt, struct iommu_domain *domain); -int iopt_table_enforce_group_resv_regions(struct io_pagetable *iopt,
struct device *device,struct iommu_group *group,phys_addr_t *sw_msi_start);+int iopt_table_enforce_dev_resv_regions(struct io_pagetable *iopt,
struct device *dev,phys_addr_t *sw_msi_start);Perhaps a silly question. The reserved regions are enforced in IOVA when a device is added to the igroup's device list. Should it be released after the device is removed from the list?
Yes, it is, iommufd_hw_pagetable_detach() does it right after the list_del()
This may not be appropriate because the devices may share some common reserved regions, such as the IOMMU_RESV_MSI.
Common reserved regions are duplicated for every device just as they were duplicated for every group.
The duplicates are keyed with an owner that is equal to the 'struct device *' so we only remove the IOVA specific to the struct device.
The interval tree effectively unions the duplicated and overlapping IOVA regions during lookup.
It is done this way to avoid memory allocation on destruction paths. We never have to chop up merged IOVA regions or something to remove a device.
Ah! Yes. This has been considered. I should read further into iopt_reserve_iova() and iopt_remove_reserved_iova(). Thanks for the explanation.
Best regards, baolu