Commit 868720fe authored by Lu Baolu's avatar Lu Baolu Committed by Joerg Roedel
Browse files

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: default avatarLu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250430021135.2370244-3-baolu.lu@linux.intel.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent f93b4ac5

drivers/iommu/intel/dmar.c

+1 −0
Original line number Diff line number Diff line
@@ -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",

drivers/iommu/intel/iommu.c

+4 −8
Original line number Diff line number Diff line
@@ -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)

drivers/iommu/intel/iommu.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */