[rfcv2,11/20] intel_iommu: Check for compatibility with IOMMUFD backed device when x-flts=on

Commit Message

Duan, Zhenzhong Feb. 19, 2025, 8:22 a.m. UTC

When vIOMMU is configured x-flts=on in scalable mode, stage-1 page table
is passed to host to construct nested page table. We need to check
compatibility of some critical IOMMU capabilities between vIOMMU and
host IOMMU to ensure guest stage-1 page table could be used by host.

For instance, vIOMMU supports stage-1 1GB huge page mapping, but host
does not, then this IOMMUFD backed device should be failed.

Declare an enum type host_iommu_device_iommu_hw_info_type aliased to
iommu_hw_info_type which come from iommufd header file. This can avoid
build failure on windows which doesn't support iommufd.

Signed-off-by: Yi Liu <[e-mail]>
Signed-off-by: Zhenzhong Duan <[e-mail]>
---
 include/system/host_iommu_device.h | 13 ++++++++++++
 hw/i386/intel_iommu.c              | 34 ++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

Patch

diff --git a/include/system/host_iommu_device.h b/include/system/host_iommu_device.h
index 250600fc1d..aa3885d7ee 100644
--- a/include/system/host_iommu_device.h
+++ b/include/system/host_iommu_device.h
@@ -133,5 +133,18 @@  struct HostIOMMUDeviceClass {
 #define HOST_IOMMU_DEVICE_CAP_FS1GP             3
 #define HOST_IOMMU_DEVICE_CAP_ERRATA            4
 
+/**
+ * enum host_iommu_device_iommu_hw_info_type - IOMMU Hardware Info Types
+ * @HOST_IOMMU_DEVICE_IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not
+ *                                             report hardware info
+ * @HOST_IOMMU_DEVICE_IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type
+ *
+ * This is alias to enum iommu_hw_info_type but for general purpose.
+ */
+enum host_iommu_device_iommu_hw_info_type {
+    HOST_IOMMU_DEVICE_IOMMU_HW_INFO_TYPE_NONE,
+    HOST_IOMMU_DEVICE_IOMMU_HW_INFO_TYPE_INTEL_VTD,
+};
+
 #define HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX       64
 #endif
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 7709f55be5..9de60e607d 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -39,6 +39,7 @@ 
 #include "kvm/kvm_i386.h"
 #include "migration/vmstate.h"
 #include "trace.h"
+#include "system/iommufd.h"
 
 /* context entry operations */
 #define VTD_CE_GET_RID2PASID(ce) \
@@ -4346,6 +4347,39 @@  static bool vtd_check_hiod(IntelIOMMUState *s, HostIOMMUDevice *hiod,
         return true;
     }
 
+    /* Remaining checks are all stage-1 translation specific */
+    if (!object_dynamic_cast(OBJECT(hiod), TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
+        error_setg(errp, "Need IOMMUFD backend when x-flts=on");
+        return false;
+    }
+
+    ret = hiodc->get_cap(hiod, HOST_IOMMU_DEVICE_CAP_IOMMU_TYPE, errp);
+    if (ret < 0) {
+        return false;
+    }
+    if (ret != HOST_IOMMU_DEVICE_IOMMU_HW_INFO_TYPE_INTEL_VTD) {
+        error_setg(errp, "Incompatible host platform IOMMU type %d", ret);
+        return false;
+    }
+
+    ret = hiodc->get_cap(hiod, HOST_IOMMU_DEVICE_CAP_NESTING, errp);
+    if (ret < 0) {
+        return false;
+    }
+    if (ret != 1) {
+        error_setg(errp, "Host IOMMU doesn't support nested translation");
+        return false;
+    }
+
+    ret = hiodc->get_cap(hiod, HOST_IOMMU_DEVICE_CAP_FS1GP, errp);
+    if (ret < 0) {
+        return false;
+    }
+    if (s->fs1gp && ret != 1) {
+        error_setg(errp, "Stage-1 1GB huge page is unsupported by host IOMMU");
+        return false;
+    }
+
     error_setg(errp, "host device is uncompatible with stage-1 translation");
     return false;
 }