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>

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)

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;

include/linux/dmar.h

@@ -26,6 +26,7 @@
 #include <linux/msi.h>
 #include <linux/irqreturn.h>
 #include <linux/rwsem.h>
+#include <linux/rcupdate.h>
 
 struct acpi_dmar_header;
 
@@ -41,7 +42,7 @@ struct dmar_drhd_unit {
 	struct list_head list;		/* list of drhd units	*/
 	struct  acpi_dmar_header *hdr;	/* ACPI header		*/
 	u64	reg_base_addr;		/* register base address*/
-	struct	pci_dev **devices; 	/* target device array	*/
+	struct	pci_dev __rcu **devices;/* target device array	*/
 	int	devices_cnt;		/* target device count	*/
 	u16	segment;		/* PCI domain		*/
 	u8	ignored:1; 		/* ignore drhd		*/
@@ -53,22 +54,31 @@ extern struct rw_semaphore dmar_global_lock;
 extern struct list_head dmar_drhd_units;
 
 #define for_each_drhd_unit(drhd) \
-	list_for_each_entry(drhd, &dmar_drhd_units, list)
+	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)
 
 #define for_each_active_drhd_unit(drhd)					\
-	list_for_each_entry(drhd, &dmar_drhd_units, list)		\
+	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\
 		if (drhd->ignored) {} else
 
 #define for_each_active_iommu(i, drhd)					\
-	list_for_each_entry(drhd, &dmar_drhd_units, list)		\
+	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\
 		if (i=drhd->iommu, drhd->ignored) {} else
 
 #define for_each_iommu(i, drhd)						\
-	list_for_each_entry(drhd, &dmar_drhd_units, list)		\
+	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\
 		if (i=drhd->iommu, 0) {} else 
 
+static inline bool dmar_rcu_check(void)
+{
+	return rwsem_is_locked(&dmar_global_lock) ||
+	       system_state == SYSTEM_BOOTING;
+}
+
+#define	dmar_rcu_dereference(p)	rcu_dereference_check((p), dmar_rcu_check())
+
 #define	for_each_dev_scope(a, c, p, d)	\
-	for ((p) = 0; ((d) = (p) < (c) ? (a)[(p)] : NULL, (p) < (c)); (p)++)
+	for ((p) = 0; ((d) = (p) < (c) ? dmar_rcu_dereference((a)[(p)]) : \
+			NULL, (p) < (c)); (p)++)
 
 #define	for_each_active_dev_scope(a, c, p, d)	\
 	for_each_dev_scope((a), (c), (p), (d))	if (!(d)) { continue; } else
@@ -78,6 +88,7 @@ extern int dmar_dev_scope_init(void);
 extern int dmar_parse_dev_scope(void *start, void *end, int *cnt,
 				struct pci_dev ***devices, u16 segment);
 extern void *dmar_alloc_dev_scope(void *start, void *end, int *cnt);
+extern void dmar_free_dev_scope(struct pci_dev __rcu ***devices, int *cnt);
 extern void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt);
 
 /* Intel IOMMU detection */