iommu/vt-d: Use RCU to protect global resources in interrupt context

Global DMA and interrupt remapping resources may be accessed in
interrupt context, so use RCU instead of rwsem to protect them
in such cases.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 50d639a2df88..e1679a6fe468 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -385,14 +385,14 @@ struct dmar_rmrr_unit {
 	struct acpi_dmar_header *hdr;	/* ACPI header		*/
 	u64	base_address;		/* reserved base address*/
 	u64	end_address;		/* reserved end address */
-	struct pci_dev **devices;	/* target devices */
+	struct pci_dev __rcu **devices;	/* target devices */
 	int	devices_cnt;		/* target device count */
 };
 
 struct dmar_atsr_unit {
 	struct list_head list;		/* list of ATSR units */
 	struct acpi_dmar_header *hdr;	/* ACPI header */
-	struct pci_dev **devices;	/* target devices */
+	struct pci_dev __rcu **devices;	/* target devices */
 	int devices_cnt;		/* target device count */
 	u8 include_all:1;		/* include all ports */
 };
@@ -634,12 +634,15 @@ static void domain_update_iommu_superpage(struct dmar_domain *domain)
 	}
 
 	/* set iommu_superpage to the smallest common denominator */
+	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd) {
 		mask &= cap_super_page_val(iommu->cap);
 		if (!mask) {
 			break;
 		}
 	}
+	rcu_read_unlock();
+
 	domain->iommu_superpage = fls(mask);
 }
 
@@ -658,6 +661,7 @@ static struct intel_iommu *device_to_iommu(int segment, u8 bus, u8 devfn)
 	struct pci_dev *dev;
 	int i;
 
+	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd) {
 		if (segment != drhd->segment)
 			continue;
@@ -677,6 +681,7 @@ static struct intel_iommu *device_to_iommu(int segment, u8 bus, u8 devfn)
 	}
 	iommu = NULL;
 out:
+	rcu_read_unlock();
 
 	return iommu;
 }
@@ -1535,10 +1540,12 @@ static void domain_exit(struct dmar_domain *domain)
 	dma_pte_free_pagetable(domain, 0, DOMAIN_MAX_PFN(domain->gaw));
 
 	/* clear attached or cached domains */
+	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd)
 		if (domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE ||
 		    test_bit(iommu->seq_id, domain->iommu_bmp))
 			iommu_detach_domain(domain, iommu);
+	rcu_read_unlock();
 
 	free_domain_mem(domain);
 }
@@ -2338,6 +2345,7 @@ static bool device_has_rmrr(struct pci_dev *dev)
 	struct pci_dev *tmp;
 	int i;
 
+	rcu_read_lock();
 	for_each_rmrr_units(rmrr) {
 		/*
 		 * Return TRUE if this RMRR contains the device that
@@ -2346,9 +2354,11 @@ static bool device_has_rmrr(struct pci_dev *dev)
 		for_each_active_dev_scope(rmrr->devices,
 					  rmrr->devices_cnt, i, tmp)
 			if (tmp == dev) {
+				rcu_read_unlock();
 				return true;
 			}
 	}
+	rcu_read_unlock();
 	return false;
 }
 
@@ -3512,7 +3522,7 @@ int __init dmar_parse_one_atsr(struct acpi_dmar_header *hdr)
 	atsru->hdr = hdr;
 	atsru->include_all = atsr->flags & 0x1;
 
-	list_add(&atsru->list, &dmar_atsr_units);
+	list_add_rcu(&atsru->list, &dmar_atsr_units);
 
 	return 0;
 }
@@ -3574,6 +3584,7 @@ int dmar_find_matched_atsr_unit(struct pci_dev *dev)
 	if (!bridge)
 		return 0;
 
+	rcu_read_lock();
 	list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) {
 		atsr = container_of(atsru->hdr, struct acpi_dmar_atsr, header);
 		if (atsr->segment != pci_domain_nr(dev->bus))
@@ -3588,6 +3599,7 @@ int dmar_find_matched_atsr_unit(struct pci_dev *dev)
 	}
 	ret = 0;
 out:
+	rcu_read_unlock();
 
 	return ret;
 }
@@ -3604,7 +3616,7 @@ int __init dmar_parse_rmrr_atsr_dev(void)
 			return ret;
 	}
 
-	list_for_each_entry(atsr, &dmar_atsr_units, list) {
+	list_for_each_entry_rcu(atsr, &dmar_atsr_units, list) {
 		ret = atsr_parse_dev(atsr);
 		if (ret)
 			return ret;