[PATCH v2 5/5] intel_iommu: Check for compatibility with iommufd backed device

[Zhenzhong Duan]

Currently only stage-2 translation is supported which is backed by
shadow page table on host side. So we don't need exact matching of
each bit of cap/ecap between vIOMMU and host. However, we can still
ensure compatibility of host and vIOMMU's address width at least,
i.e., vIOMMU's aw-bits <= host IOMMU aw-bits, which is missed before.

When stage-1 translation is supported in future, a.k.a. scalable
modern mode, this mechanism will be further extended to check more
bits.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 include/hw/i386/intel_iommu.h |  1 +
 hw/i386/intel_iommu.c         | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index bbc7b96add..2bbde41e45 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -47,6 +47,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(IntelIOMMUState, 
INTEL_IOMMU_DEVICE)
 #define VTD_HOST_AW_48BIT           48
 #define VTD_HOST_ADDRESS_WIDTH      VTD_HOST_AW_39BIT
 #define VTD_HAW_MASK(aw)            ((1ULL << (aw)) - 1)
+#define VTD_MGAW_FROM_CAP(cap)      ((cap >> 16) & 0x3fULL)
 
 #define DMAR_REPORT_F_INTR          (1)
 
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index d2cd186df0..d8fac9ef9f 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3846,6 +3846,29 @@ static int vtd_check_iommufd_hdev(IntelIOMMUState *s,
                                   HostIOMMUDevice *hiod,
                                   Error **errp)
 {
+    HostIOMMUDeviceClass *hiodc = HOST_IOMMU_DEVICE_GET_CLASS(hiod);
+    struct iommu_hw_info_vtd *vtd;
+    HIOD_IOMMUFD_INFO info;
+    int host_aw_bits, ret;
+
+    ret = hiodc->get_host_iommu_info(hiod, &info, sizeof(info), errp);
+    if (ret) {
+        return ret;
+    }
+
+    if (info.type != IOMMU_HW_INFO_TYPE_INTEL_VTD) {
+        error_setg(errp, "IOMMU hardware is not compatible");
+        return -EINVAL;
+    }
+
+    vtd = &info.data.vtd;
+    host_aw_bits = VTD_MGAW_FROM_CAP(vtd->cap_reg) + 1;
+    if (s->aw_bits > host_aw_bits) {
+        error_setg(errp, "aw-bits %d > host aw-bits %d",
+                   s->aw_bits, host_aw_bits);
+        return -EINVAL;
+    }
+
     return 0;
 }
 
-- 
2.34.1