AMD IOMMU: add device reference counting for protection domains

Impact: know how many devices are assigned to a domain
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/include/asm/amd_iommu_types.h

@@ -203,6 +203,7 @@ struct protection_domain {
 	int mode;		/* paging mode (0-6 levels) */
 	u64 *pt_root;		/* page table root pointer */
 	unsigned long flags;	/* flags to find out type of domain */
+	unsigned dev_cnt;	/* devices assigned to this domain */
 	void *priv;		/* private data */
 };
 

arch/x86/kernel/amd_iommu.c

@@ -825,9 +825,10 @@ static void set_device_domain(struct amd_iommu *iommu,
 			      u16 devid)
 {
 	unsigned long flags;
-
 	u64 pte_root = virt_to_phys(domain->pt_root);
 
+	domain->dev_cnt += 1;
+
 	pte_root |= (domain->mode & DEV_ENTRY_MODE_MASK)
 		    << DEV_ENTRY_MODE_SHIFT;
 	pte_root |= IOMMU_PTE_IR | IOMMU_PTE_IW | IOMMU_PTE_P | IOMMU_PTE_TV;