[PATCH v5 14/21] intel_iommu: Stick to system MR for IOMMUFD backed host device when x-fls=on

[Zhenzhong Duan <zhenzhong.duan@intel.com>]

When guest in scalable mode and x-flts=on, we stick to system MR for IOMMUFD
backed host device. Then its default hwpt contains GPA->HPA mappings which is
used directly if PGTT=PT and used as nested parent if PGTT=FLT. Otherwise
fallback to original processing.

Suggested-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 hw/i386/intel_iommu.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index af384ce7f0..15582977b8 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1773,6 +1773,28 @@ static bool vtd_dev_pt_enabled(IntelIOMMUState *s, VTDContextEntry *ce,
 
 }
 
+static VTDHostIOMMUDevice *vtd_find_hiod_iommufd(IntelIOMMUState *s,
+                                                 VTDAddressSpace *as)
+{
+    struct vtd_as_key key = {
+        .bus = as->bus,
+        .devfn = as->devfn,
+    };
+    VTDHostIOMMUDevice *vtd_hiod = g_hash_table_lookup(s->vtd_host_iommu_dev,
+                                                       &key);
+
+    if (vtd_hiod && vtd_hiod->hiod &&
+        object_dynamic_cast(OBJECT(vtd_hiod->hiod),
+                            TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
+        return vtd_hiod;
+    }
+    return NULL;
+}
+
+/*
+ * vtd_switch_address_space() calls vtd_as_pt_enabled() to determine which
+ * MR to switch to. Switch to system MR if return true, iommu MR otherwise.
+ */
 static bool vtd_as_pt_enabled(VTDAddressSpace *as)
 {
     IntelIOMMUState *s;
@@ -1781,6 +1803,18 @@ static bool vtd_as_pt_enabled(VTDAddressSpace *as)
     assert(as);
 
     s = as->iommu_state;
+
+    /*
+     * When guest in scalable mode and x-flts=on, we stick to system MR
+     * for IOMMUFD backed host device. Then its default hwpt contains
+     * GPA->HPA mappings which is used directly if PGTT=PT and used as
+     * nested parent if PGTT=FLT. Otherwise fallback to original
+     * processing.
+     */
+    if (s->root_scalable && s->flts && vtd_find_hiod_iommufd(s, as)) {
+        return true;
+    }
+
     if (vtd_dev_to_context_entry(s, pci_bus_num(as->bus), as->devfn,
                                  &ce)) {
         /*
-- 
2.47.1