iommu/vt-d: Replace spin_lock with mutex to protect domain ida

The domain ID allocator is currently protected by a spin_lock. However,
ida_alloc_range can potentially block if it needs to allocate memory to
grow its internal structures.

Replace the spin_lock with a mutex which allows sleep on block. Thus,
the memory allocation flags can be updated from GFP_ATOMIC to GFP_KERNEL
to allow blocking memory allocations if necessary.

Introduce a new mutex, did_lock, specifically for protecting the domain
ida. The existing spinlock will remain for protecting other intel_iommu
fields.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250430021135.2370244-3-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 0e35969c026bbf9c0b4ffdedcf7a1a639e4e993e..9e17e8e563089bfe4b40c19029e93e013fa9e0b0 100644 (file)
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1101,6 +1101,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
        iommu->node = NUMA_NO_NODE;
        spin_lock_init(&iommu->lock);
        ida_init(&iommu->domain_ida);
+       mutex_init(&iommu->did_lock);
 
        ver = readl(iommu->reg + DMAR_VER_REG);
        pr_info("%s: reg_base_addr %llx ver %d:%d cap %llx ecap %llx\n",

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 023105234139251c7e61da7210e0a8d81d36e0f9..0f2845147058d5a6443fbc0c35bbe8b6b05b2650 100644 (file)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1345,17 +1345,16 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
        if (!info)
                return -ENOMEM;
 
-       spin_lock(&iommu->lock);
+       guard(mutex)(&iommu->did_lock);
        curr = xa_load(&domain->iommu_array, iommu->seq_id);
        if (curr) {
                curr->refcnt++;
-               spin_unlock(&iommu->lock);
                kfree(info);
                return 0;
        }
 
        num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID,
-                             cap_ndoms(iommu->cap) - 1, GFP_ATOMIC);
+                             cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
        if (num < 0) {
                pr_err("%s: No free domain ids\n", iommu->name);
                goto err_unlock;
@@ -1365,19 +1364,17 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
        info->did       = num;
        info->iommu     = iommu;
        curr = xa_cmpxchg(&domain->iommu_array, iommu->seq_id,
-                         NULL, info, GFP_ATOMIC);
+                         NULL, info, GFP_KERNEL);
        if (curr) {
                ret = xa_err(curr) ? : -EBUSY;
                goto err_clear;
        }
 
-       spin_unlock(&iommu->lock);
        return 0;
 
 err_clear:
        ida_free(&iommu->domain_ida, info->did);
 err_unlock:
-       spin_unlock(&iommu->lock);
        kfree(info);
        return ret;
 }
@@ -1389,7 +1386,7 @@ void domain_detach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
        if (domain->domain.type == IOMMU_DOMAIN_SVA)
                return;
 
-       spin_lock(&iommu->lock);
+       guard(mutex)(&iommu->did_lock);
        info = xa_load(&domain->iommu_array, iommu->seq_id);
        if (--info->refcnt == 0) {
                ida_free(&iommu->domain_ida, info->did);
@@ -1397,7 +1394,6 @@ void domain_detach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
                domain->nid = NUMA_NO_NODE;
                kfree(info);
        }
-       spin_unlock(&iommu->lock);
 }
 
 static void domain_exit(struct dmar_domain *domain)

diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index 25faf3aadd2469e71fc4e258e55dbd8b99a0519b..5f140892fae008ef222ae649de43ca427245f95e 100644 (file)
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -722,6 +722,8 @@ struct intel_iommu {
        unsigned char   name[16];    /* Device Name */
 
 #ifdef CONFIG_INTEL_IOMMU
+       /* mutex to protect domain_ida */
+       struct mutex    did_lock;
        struct ida      domain_ida; /* domain id allocator */
        unsigned long   *copied_tables; /* bitmap of copied tables */
        spinlock_t      lock; /* protect context, domain ids */