[PATCH v2 18/20] amd_iommu: Toggle address translation mode on devtab entry invalidation

[Alejandro Jimenez <alejandro.j.jimenez@oracle.com>]

A guest must issue an INVALIDATE_DEVTAB_ENTRY command after changing a
Device Table entry (DTE) e.g. after attaching a device and setting up its
DTE. When intercepting this event, determine if the DTE has been configured
for paging or not, and toggle the appropriate memory regions to allow DMA
address translation for the address space if needed. Requires dma-remap=on.

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
---
 hw/i386/amd_iommu.c | 78 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index a2df73062bf7..75a92067f35f 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -991,18 +991,92 @@ static void amdvi_switch_address_space_all(AMDVIState *s)
     }
 }
 
+/*
+ * A guest driver must issue the INVALIDATE_DEVTAB_ENTRY command to the IOMMU
+ * after changing a Device Table entry. We can use this fact to detect when a
+ * Device Table entry is created for a device attached to a paging domain and
+ * enable the corresponding IOMMU memory region to allow for DMA translation if
+ * appropriate.
+ */
+static void amdvi_update_addr_translation_mode(AMDVIState *s, uint16_t devid)
+{
+    uint8_t bus_num, devfn, dte_mode;
+    AMDVIAddressSpace *as;
+    uint64_t dte[4] = { 0 };
+    IOMMUNotifier *n;
+    int ret;
+
+    /*
+     * Convert the devid encoded in the command to a bus and devfn in
+     * order to retrieve the corresponding address space.
+     */
+    bus_num = PCI_BUS_NUM(devid);
+    devfn = devid & 0xff;
+
+    /*
+     * The main buffer of size (AMDVIAddressSpace *) * (PCI_BUS_MAX) has already
+     * been allocated within AMDVIState, but must be careful to not access
+     * unallocated devfn.
+     */
+    if (!s->address_spaces[bus_num] || !s->address_spaces[bus_num][devfn]) {
+        return;
+    }
+    as = s->address_spaces[bus_num][devfn];
+
+    ret = amdvi_as_to_dte(as, dte);
+
+    if (!ret) {
+        dte_mode = (dte[0] >> AMDVI_DEV_MODE_RSHIFT) & AMDVI_DEV_MODE_MASK;
+    }
+
+    if ((ret < 0) || (!ret && !dte_mode)) {
+        /*
+         * The DTE could not be retrieved, it is not valid, or it is not setup
+         * for paging. In either case, ensure that if paging was previously in
+         * use then invalidate all existing mappings and then switch to use the
+         * no_dma memory region.
+         */
+        if (as->addr_translation) {
+            as->addr_translation = false;
+
+            IOMMU_NOTIFIER_FOREACH(n, &as->iommu) {
+                amdvi_address_space_unmap(as, n);
+            }
+            amdvi_switch_address_space(as);
+        }
+    } else if (!as->addr_translation) {
+        /*
+         * Installing a DTE that enables translation where it wasn't previously
+         * active. Activate the DMA memory region.
+         */
+        as->addr_translation = true;
+        amdvi_switch_address_space(as);
+        amdvi_address_space_sync(as);
+    }
+}
+
 /* log error without aborting since linux seems to be using reserved bits */
 static void amdvi_inval_devtab_entry(AMDVIState *s, uint64_t *cmd)
 {
     uint16_t devid = cpu_to_le16((uint16_t)extract64(cmd[0], 0, 16));
 
+    trace_amdvi_devtab_inval(PCI_BUS_NUM(devid), PCI_SLOT(devid),
+                             PCI_FUNC(devid));
+
     /* This command should invalidate internal caches of which there isn't */
     if (extract64(cmd[0], 16, 44) || cmd[1]) {
         amdvi_log_illegalcom_error(s, extract64(cmd[0], 60, 4),
                                    s->cmdbuf + s->cmdbuf_head);
+        return;
+    }
+
+    /*
+     * When DMA remapping capability is enabled, check if updated DTE is setup
+     * for paging or not, and configure the corresponding memory regions.
+     */
+    if (s->dma_remap) {
+        amdvi_update_addr_translation_mode(s, devid);
     }
-    trace_amdvi_devtab_inval(PCI_BUS_NUM(devid), PCI_SLOT(devid),
-                             PCI_FUNC(devid));
 }
 
 static void amdvi_complete_ppr(AMDVIState *s, uint64_t *cmd)
-- 
2.43.5