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>

2 files changed, 36 insertions, 17 deletions

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index c9aca8841fa..6e4d851991f 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -71,13 +71,13 @@ static void __init dmar_register_drhd_unit(struct dmar_drhd_unit *drhd)
 	 * the very end.
 	 */
 	if (drhd->include_all)
-		list_add_tail(&drhd->list, &dmar_drhd_units);
+		list_add_tail_rcu(&drhd->list, &dmar_drhd_units);
 	else
-		list_add(&drhd->list, &dmar_drhd_units);
+		list_add_rcu(&drhd->list, &dmar_drhd_units);
 }
 
 static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
-					   struct pci_dev **dev, u16 segment)
+					   struct pci_dev __rcu **dev, u16 segment)
 {
 	struct pci_bus *bus;
 	struct pci_dev *pdev = NULL;
@@ -122,7 +122,9 @@ static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
 			pci_name(pdev));
 		return -EINVAL;
 	}
-	*dev = pdev;
+
+	rcu_assign_pointer(*dev, pdev);
+
 	return 0;
 }
 
@@ -149,7 +151,7 @@ void *dmar_alloc_dev_scope(void *start, void *end, int *cnt)
 }
 
 int __init dmar_parse_dev_scope(void *start, void *end, int *cnt,
-				struct pci_dev ***devices, u16 segment)
+				struct pci_dev __rcu ***devices, u16 segment)
 {
 	struct acpi_dmar_device_scope *scope;
 	int index, ret;
@@ -177,7 +179,7 @@ int __init dmar_parse_dev_scope(void *start, void *end, int *cnt,
 	return 0;
 }
 
-void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt)
+void dmar_free_dev_scope(struct pci_dev __rcu ***devices, int *cnt)
 {
 	int i;
 	struct pci_dev *tmp_dev;
@@ -186,9 +188,10 @@ void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt)
 		for_each_active_dev_scope(*devices, *cnt, i, tmp_dev)
 			pci_dev_put(tmp_dev);
 		kfree(*devices);
-		*devices = NULL;
-		*cnt = 0;
 	}
+
+	*devices = NULL;
+	*cnt = 0;
 }
 
 /**
@@ -410,7 +413,7 @@ parse_dmar_table(void)
 	return ret;
 }
 
-static int dmar_pci_device_match(struct pci_dev *devices[], int cnt,
+static int dmar_pci_device_match(struct pci_dev __rcu *devices[], int cnt,
 			  struct pci_dev *dev)
 {
 	int index;
@@ -431,11 +434,12 @@ static int dmar_pci_device_match(struct pci_dev *devices[], int cnt,
 struct dmar_drhd_unit *
 dmar_find_matched_drhd_unit(struct pci_dev *dev)
 {
-	struct dmar_drhd_unit *dmaru = NULL;
+	struct dmar_drhd_unit *dmaru;
 	struct acpi_dmar_hardware_unit *drhd;
 
 	dev = pci_physfn(dev);
 
+	rcu_read_lock();
 	for_each_drhd_unit(dmaru) {
 		drhd = container_of(dmaru->hdr,
 				    struct acpi_dmar_hardware_unit,
@@ -443,14 +447,17 @@ dmar_find_matched_drhd_unit(struct pci_dev *dev)
 
 		if (dmaru->include_all &&
 		    drhd->segment == pci_domain_nr(dev->bus))
-			return dmaru;
+			goto out;
 
 		if (dmar_pci_device_match(dmaru->devices,
 					  dmaru->devices_cnt, dev))
-			return dmaru;
+			goto out;
 	}
+	dmaru = NULL;
+out:
+	rcu_read_unlock();
 
-	return NULL;
+	return dmaru;
 }
 
 int __init dmar_dev_scope_init(void)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 50d639a2df8..e1679a6fe46 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;