On 2025/8/22 14:40, Zhenzhong Duan wrote:
When vIOMMU is configured x-flts=on in scalable mode, stage-1 page table
is passed to host to construct nested page table.
for passthrough devices :)
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 fail.
do you have a list of what caps should be checked to ensure guest
stage-1 page table work on hw? I can see EAFS. But it is not yet exposed
to guest, so no need to check it for now.
Even of the checks pass, for now we willingly reject the association
because all the bits are not there yet.
better call out it would be relaxed in the end of this series. Otherwise
it's a little confused. :)
Signed-off-by: Yi Liu <yi.l....@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
---
hw/i386/intel_iommu_internal.h | 1 +
hw/i386/intel_iommu.c | 30 +++++++++++++++++++++++++++++-
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index c7046eb4e2..f7510861d1 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -192,6 +192,7 @@
#define VTD_ECAP_PT (1ULL << 6)
#define VTD_ECAP_SC (1ULL << 7)
#define VTD_ECAP_MHMV (15ULL << 20)
+#define VTD_ECAP_NEST (1ULL << 26)
#define VTD_ECAP_SRS (1ULL << 31)
#define VTD_ECAP_PSS (7ULL << 35) /* limit: MemTxAttrs::pid */
#define VTD_ECAP_PASID (1ULL << 40)
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 512ca4fdc5..da355bda79 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -40,6 +40,7 @@
#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) \
@@ -4366,7 +4367,34 @@ static bool vtd_check_hiod(IntelIOMMUState *s,
HostIOMMUDevice *hiod,
return true;
}
- error_setg(errp, "host device is uncompatible with stage-1 translation");
+#ifdef CONFIG_IOMMUFD
+ struct HostIOMMUDeviceCaps *caps = &hiod->caps;
+ struct iommu_hw_info_vtd *vtd = &caps->vendor_caps.vtd;
+
+ /* 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;
+ }
+
+ if (caps->type != IOMMU_HW_INFO_TYPE_INTEL_VTD) {
+ error_setg(errp, "Incompatible host platform IOMMU type %d",
+ caps->type);
+ return false;
+ }
+
+ if (!(vtd->ecap_reg & VTD_ECAP_NEST)) {
+ error_setg(errp, "Host IOMMU doesn't support nested translation");
+ return false;
+ }
this check may be already been covered by the sync in patch 05 as
the set_iommu_device op is called after attach_device. If no NESTED cap,
allocating nested hwpt would be failed.
+
+ if (s->fs1gp && !(vtd->cap_reg & VTD_CAP_FS1GP)) {
+ error_setg(errp, "Stage-1 1GB huge page is unsupported by host IOMMU");
s/huge page/large page/ as VT-d spec use large page.
+ return false;
+ }
+#endif > +
+ error_setg(errp, "host IOMMU is incompatible with stage-1 translation");
s/stage-1 translation/guest stage-1 translation/
return false;
}
with above minor nits done, the patch looks good to me. Hence,
Reviewed-by: Yi Liu <yi.l....@intel.com>
