iommu/amd: Remove protection_domain.dev_cnt variable

protection_domain->dev_list tracks list of attached devices to
domain. We can use list_* functions on dev_list to get device count.
Hence remove 'dev_cnt' variable.

No functional change intended.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20241030063556.6104-4-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: hegdevasant

drivers/iommu/amd/amd_iommu_types.h

@@ -578,7 +578,6 @@ struct protection_domain {
 	u16 id;			/* the domain id written to the device table */
 	enum protection_domain_mode pd_mode; /* Track page table type */
 	bool dirty_tracking;	/* dirty tracking is enabled in the domain */
-	unsigned dev_cnt;	/* devices assigned to this domain */
 	unsigned dev_iommu[MAX_IOMMUS]; /* per-IOMMU reference count */
 
 	struct mmu_notifier mn;	/* mmu notifier for the SVA domain */

drivers/iommu/amd/iommu.c

@@ -2031,7 +2031,6 @@ static int do_attach(struct iommu_dev_data *dev_data,
 
 	/* Do reference counting */
 	domain->dev_iommu[iommu->index] += 1;
-	domain->dev_cnt                 += 1;
 
 	/* Setup GCR3 table */
 	if (pdom_is_sva_capable(domain)) {
@@ -2064,7 +2063,6 @@ static void do_detach(struct iommu_dev_data *dev_data)
 
 	/* decrease reference counters - needs to happen after the flushes */
 	domain->dev_iommu[iommu->index] -= 1;
-	domain->dev_cnt                 -= 1;
 }
 
 /*
@@ -2237,16 +2235,13 @@ static void cleanup_domain(struct protection_domain *domain)
 
 	lockdep_assert_held(&domain->lock);
 
-	if (!domain->dev_cnt)
-		return;
-
 	while (!list_empty(&domain->dev_list)) {
 		entry = list_first_entry(&domain->dev_list,
 					 struct iommu_dev_data, list);
 		BUG_ON(!entry->domain);
 		do_detach(entry);
 	}
-	WARN_ON(domain->dev_cnt != 0);
+	WARN_ON(!list_empty(&domain->dev_list));
 }
 
 void protection_domain_free(struct protection_domain *domain)