On 2025/8/22 14:40, Zhenzhong Duan wrote:
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....@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.d...@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;
+ }
+
I think you'd add this logic in vtd_switch_address_space() as the return
value of this helper is to reflect if guest has enabled pt. It may break
logic in the caller side.
Regards,
Yi Liu
if (vtd_dev_to_context_entry(s, pci_bus_num(as->bus), as->devfn,
&ce)) {
/*
