iommu: Move global PASID allocation from SVA to core

Intel ENQCMD requires a single PASID to be shared between multiple
devices, as the PASID is stored in a single MSR register per-process
and userspace can use only that one PASID.

This means that the PASID allocation for any ENQCMD using device driver
must always come from a shared global pool, regardless of what kind of
domain the PASID will be used with.

Split the code for the global PASID allocator into
iommu_alloc/free_global_pasid() so that drivers can attach non-SVA
domains to PASIDs as well.

This patch moves global PASID allocation APIs from SVA to IOMMU APIs.
Reserved PASIDs, currently only RID_PASID, are excluded from the global
PASID allocation.

It is expected that device drivers will use the allocated PASIDs to
attach to appropriate IOMMU domains for use.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lore.kernel.org/r/20230802212427.1497170-3-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2870bc29d456..6b821cb715d5 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -197,6 +197,7 @@ enum iommu_dev_features {
 };
 
 #define IOMMU_NO_PASID	(0U) /* Reserved for DMA w/o PASID */
+#define IOMMU_FIRST_GLOBAL_PASID	(1U) /*starting range for allocation */
 #define IOMMU_PASID_INVALID	(-1U)
 typedef unsigned int ioasid_t;
 
@@ -728,6 +729,8 @@ void iommu_detach_device_pasid(struct iommu_domain *domain,
 struct iommu_domain *
 iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid,
 			       unsigned int type);
+ioasid_t iommu_alloc_global_pasid(struct device *dev);
+void iommu_free_global_pasid(ioasid_t pasid);
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
@@ -1089,6 +1092,13 @@ iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid,
 {
 	return NULL;
 }
+
+static inline ioasid_t iommu_alloc_global_pasid(struct device *dev)
+{
+	return IOMMU_PASID_INVALID;
+}
+
+static inline void iommu_free_global_pasid(ioasid_t pasid) {}
 #endif /* CONFIG_IOMMU_API */
 
 /**