amd_iommu: Unmap all address spaces under the AMD IOMMU on reset

Support dropping all existing mappings on reset. When the guest kernel
reboots it will create new ones, but other components that run before
the kernel (e.g. OVMF) should not be able to use existing mappings from
the previous boot.

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250919213515.917111-13-alejandro.j.jimenez@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 74 insertions, 0 deletions

diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index 4376e977f8..497f18c540 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -847,6 +847,77 @@ next:
     }
 }
 
+/*
+ * Unmap entire range that the notifier registered for i.e. the full AS.
+ *
+ * This is seemingly technically equivalent to directly calling
+ * memory_region_unmap_iommu_notifier_range(), but it allows to check for
+ * notifier boundaries and issue notifications with ranges within those bounds.
+ */
+static void amdvi_address_space_unmap(AMDVIAddressSpace *as, IOMMUNotifier *n)
+{
+
+    hwaddr start = n->start;
+    hwaddr end = n->end;
+    hwaddr remain;
+    DMAMap map;
+
+    assert(start <= end);
+    remain = end - start + 1;
+
+    /*
+     * Divide the notifier range into chunks that are aligned and do not exceed
+     * the notifier boundaries.
+     */
+    while (remain >= AMDVI_PAGE_SIZE) {
+
+        IOMMUTLBEvent event;
+
+        uint64_t mask = dma_aligned_pow2_mask(start, end, 64);
+
+        event.type = IOMMU_NOTIFIER_UNMAP;
+
+        IOMMUTLBEntry entry = {
+            .target_as = &address_space_memory,
+            .iova = start,
+            .translated_addr = 0,   /* irrelevant for unmap case */
+            .addr_mask = mask,
+            .perm = IOMMU_NONE,
+        };
+        event.entry = entry;
+
+        /* Call notifier registered for updates on this address space */
+        memory_region_notify_iommu_one(n, &event);
+
+        start += mask + 1;
+        remain -= mask + 1;
+    }
+
+    assert(!remain);
+
+    map.iova = n->start;
+    map.size = n->end - n->start;
+
+    iova_tree_remove(as->iova_tree, map);
+}
+
+/*
+ * For all the address spaces with notifiers registered, unmap the entire range
+ * the notifier registered for i.e. clear all the address spaces managed by the
+ * IOMMU.
+ */
+static void amdvi_address_space_unmap_all(AMDVIState *s)
+{
+    AMDVIAddressSpace *as;
+    IOMMUNotifier *n;
+
+    QLIST_FOREACH(as, &s->amdvi_as_with_notifiers, next) {
+        IOMMU_NOTIFIER_FOREACH(n, &as->iommu) {
+            amdvi_address_space_unmap(as, n);
+        }
+    }
+}
+
 /* log error without aborting since linux seems to be using reserved bits */
 static void amdvi_inval_devtab_entry(AMDVIState *s, uint64_t *cmd)
 {
@@ -2099,6 +2170,9 @@ static void amdvi_sysbus_reset(DeviceState *dev)
 
     msi_reset(&s->pci->dev);
     amdvi_init(s);
+
+    /* Discard all mappings on device reset */
+    amdvi_address_space_unmap_all(s);
 }
 
 static const VMStateDescription vmstate_amdvi_sysbus_migratable = {