AMD IOMMU: don't assign preallocated protection domains to devices

In isolation mode the protection domains for the devices are
preallocated and preassigned. This is bad if a device should be passed
to a virtualization guest because the IOMMU code does not know if it is
in use by a driver. This patch changes the code to assign the device to
the preallocated domain only if there are dma mapping requests for it.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 38 insertions, 5 deletions

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index a6a6f8ed1cf5..7c1791447451 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -33,6 +33,10 @@
 
 static DEFINE_RWLOCK(amd_iommu_devtable_lock);
 
+/* A list of preallocated protection domains */
+static LIST_HEAD(iommu_pd_list);
+static DEFINE_SPINLOCK(iommu_pd_list_lock);
+
 /*
  * general struct to manage commands send to an IOMMU
  */
@@ -663,6 +667,7 @@ static struct dma_ops_domain *dma_ops_domain_alloc(struct amd_iommu *iommu,
         dma_dom->next_bit = 0;
 
         dma_dom->need_flush = false;
+        dma_dom->target_dev = 0xffff;
 
         /* Intialize the exclusion range if necessary */
         if (iommu->exclusion_start &&
@@ -769,6 +774,33 @@ static bool check_device(struct device *dev)
 }
 
 /*
+ * In this function the list of preallocated protection domains is traversed to
+ * find the domain for a specific device
+ */
+static struct dma_ops_domain *find_protection_domain(u16 devid)
+{
+        struct dma_ops_domain *entry, *ret = NULL;
+        unsigned long flags;
+
+        if (list_empty(&iommu_pd_list))
+                return NULL;
+
+        spin_lock_irqsave(&iommu_pd_list_lock, flags);
+
+        list_for_each_entry(entry, &iommu_pd_list, list) {
+                if (entry->target_dev == devid) {
+                        ret = entry;
+                        list_del(&ret->list);
+                        break;
+                }
+        }
+
+        spin_unlock_irqrestore(&iommu_pd_list_lock, flags);
+
+        return ret;
+}
+
+/*
  * In the dma_ops path we only have the struct device. This function
  * finds the corresponding IOMMU, the protection domain and the
  * requestor id for a given device.
@@ -803,9 +835,11 @@ static int get_device_resources(struct device *dev,
         *iommu = amd_iommu_rlookup_table[*bdf];
         if (*iommu == NULL)
                 return 0;
-        dma_dom = (*iommu)->default_dom;
         *domain = domain_for_device(*bdf);
         if (*domain == NULL) {
+                dma_dom = find_protection_domain(*bdf);
+                if (!dma_dom)
+                        dma_dom = (*iommu)->default_dom;
                 *domain = &dma_dom->domain;
                 set_device_domain(*iommu, *domain, *bdf);
                 printk(KERN_INFO "AMD IOMMU: Using protection domain %d for "
@@ -1257,10 +1291,9 @@ void prealloc_protection_domains(void)
                 if (!dma_dom)
                         continue;
                 init_unity_mappings_for_device(dma_dom, devid);
-                set_device_domain(iommu, &dma_dom->domain, devid);
-                printk(KERN_INFO "AMD IOMMU: Allocated domain %d for device ",
-                       dma_dom->domain.id);
-                print_devid(devid, 1);
+                dma_dom->target_dev = devid;
+
+                list_add_tail(&dma_dom->list, &iommu_pd_list);
         }
 }