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, 17 insertions, 6 deletions

diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 8f06a0135a84..bedebab934b4 100644
--- a/include/linux/dmar.h
+++ b/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 */