iommu/vt-d: Removed unused iommu_count in dmar domain

DMAR domain uses per DMAR refcount. It is indexed by iommu seq_id.
Older iommu_count is only incremented and decremented but no decisions
are taken based on this refcount. This is not of much use.

Hence, remove iommu_count and further simplify domain_detach_iommu()
by returning void.
Signed-off-by: NParav Pandit <parav@nvidia.com>
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210530075053.264218-1-parav@nvidia.com
Link: https://lore.kernel.org/r/20210610020115.1637656-21-baolu.lu@linux.intel.comSigned-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/intel/iommu.c

@@ -1920,7 +1920,6 @@ static int domain_attach_iommu(struct dmar_domain *domain,
 	assert_spin_locked(&iommu->lock);
 
 	domain->iommu_refcnt[iommu->seq_id] += 1;
-	domain->iommu_count += 1;
 	if (domain->iommu_refcnt[iommu->seq_id] == 1) {
 		ndomains = cap_ndoms(iommu->cap);
 		num      = find_first_zero_bit(iommu->domain_ids, ndomains);
@@ -1928,7 +1927,6 @@ static int domain_attach_iommu(struct dmar_domain *domain,
 		if (num >= ndomains) {
 			pr_err("%s: No free domain ids\n", iommu->name);
 			domain->iommu_refcnt[iommu->seq_id] -= 1;
-			domain->iommu_count -= 1;
 			return -ENOSPC;
 		}
 
@@ -1944,16 +1942,15 @@ static int domain_attach_iommu(struct dmar_domain *domain,
 	return 0;
 }
 
-static int domain_detach_iommu(struct dmar_domain *domain,
-			       struct intel_iommu *iommu)
+static void domain_detach_iommu(struct dmar_domain *domain,
+				struct intel_iommu *iommu)
 {
-	int num, count;
+	int num;
 
 	assert_spin_locked(&device_domain_lock);
 	assert_spin_locked(&iommu->lock);
 
 	domain->iommu_refcnt[iommu->seq_id] -= 1;
-	count = --domain->iommu_count;
 	if (domain->iommu_refcnt[iommu->seq_id] == 0) {
 		num = domain->iommu_did[iommu->seq_id];
 		clear_bit(num, iommu->domain_ids);
@@ -1962,8 +1959,6 @@ static int domain_detach_iommu(struct dmar_domain *domain,
 		domain_update_iommu_cap(domain);
 		domain->iommu_did[iommu->seq_id] = 0;
 	}
-
-	return count;
 }
 
 static inline int guestwidth_to_adjustwidth(int gaw)

include/linux/intel-iommu.h

@@ -561,7 +561,6 @@ struct dmar_domain {
 	int		agaw;
 
 	int		flags;		/* flags to find out type of domain */
-	int		iommu_count;	/* reference count of iommu */
 	int		iommu_superpage;/* Level of superpages supported:
 					   0 == 4KiB (no superpages), 1 == 2MiB,
 					   2 == 1GiB, 3 == 512GiB, 4 == 1TiB */