amd_iommu: Toggle memory regions based on address translation mode

Enable the appropriate memory region for an address space depending on the
address translation mode selected for it. This is currently based on a
generic x86 IOMMU property, and only done during the address space
initialization. Extract the code into a helper and toggle the regions based
on whether the specific address space is using address translation (via the
newly introduced addr_translation field). Later, region activation will also
be controlled by availability of DMA remapping capability (via dma-remap
property to be introduced in follow up changes).

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250919213515.917111-16-alejandro.j.jimenez@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index d74d42b3dd..67a26f5247 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -74,6 +74,8 @@ struct AMDVIAddressSpace {
     QLIST_ENTRY(AMDVIAddressSpace) next;
     /* Record DMA translation ranges */
     IOVATree *iova_tree;
+    /* DMA address translation active */
+    bool addr_translation;
 };
 
 /* AMDVI cache entry */
@@ -982,6 +984,23 @@ static void amdvi_iommu_address_space_sync_all(AMDVIState *s)
     }
 }
 
+/*
+ * Toggle between address translation and passthrough modes by enabling the
+ * corresponding memory regions.
+ */
+static void amdvi_switch_address_space(AMDVIAddressSpace *amdvi_as)
+{
+    if (amdvi_as->addr_translation) {
+        /* Enabling DMA region */
+        memory_region_set_enabled(&amdvi_as->iommu_nodma, false);
+        memory_region_set_enabled(MEMORY_REGION(&amdvi_as->iommu), true);
+    } else {
+        /* Disabling DMA region, using passthrough */
+        memory_region_set_enabled(MEMORY_REGION(&amdvi_as->iommu), false);
+        memory_region_set_enabled(&amdvi_as->iommu_nodma, true);
+    }
+}
+
 /* log error without aborting since linux seems to be using reserved bits */
 static void amdvi_inval_devtab_entry(AMDVIState *s, uint64_t *cmd)
 {
@@ -2070,6 +2089,7 @@ static AddressSpace *amdvi_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
         iommu_as[devfn]->iommu_state = s;
         iommu_as[devfn]->notifier_flags = IOMMU_NOTIFIER_NONE;
         iommu_as[devfn]->iova_tree = iova_tree_new();
+        iommu_as[devfn]->addr_translation = false;
 
         amdvi_dev_as = iommu_as[devfn];
 
@@ -2112,8 +2132,7 @@ static AddressSpace *amdvi_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
                                             AMDVI_INT_ADDR_FIRST,
                                             &amdvi_dev_as->iommu_ir, 1);
 
-        memory_region_set_enabled(&amdvi_dev_as->iommu_nodma, false);
-        memory_region_set_enabled(MEMORY_REGION(&amdvi_dev_as->iommu), true);
+        amdvi_switch_address_space(amdvi_dev_as);
     }
     return &iommu_as[devfn]->as;
 }