>-----Original Message-----
>From: Eric Auger <eric.au...@redhat.com>
>Subject: Re: [PATCH v1 03/15] intel_iommu: Check for compatibility with
>IOMMUFD backed device when x-flts=on
>
>Hi Zhenzhong,
>
>On 6/6/25 12:04 PM, 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. 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.
>>
>> 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 | 28 ++++++++++++++++++++++++++++
>> 2 files changed, 29 insertions(+)
>>
>> diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
>> index e8b211e8b0..2cda744786 100644
>> --- a/hw/i386/intel_iommu_internal.h
>> +++ b/hw/i386/intel_iommu_internal.h
>> @@ -191,6 +191,7 @@
>> #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_PASID (1ULL << 40)
>> #define VTD_ECAP_SMTS (1ULL << 43)
>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>> index a2f3250724..c42ef83ddc 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) \
>> @@ -4361,6 +4362,33 @@ static bool vtd_check_hiod(IntelIOMMUState *s,
>HostIOMMUDevice *hiod,
>> return true;
>> }
>>
>> +#ifdef CONFIG_IOMMUFD
>is it requested?
Yes, windows build needs it.
iommu_hw_info_vtd and IOMMU_HW_INFO_TYPE_INTEL_VTD are defined in
linux/iommufd.h,
meanwhile all below check take effect only when IOMMUFD is supported.
Thanks
Zhenzhong
>
>Cheers
>
>Eric
>> + 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;
>> + }
>> +
>> + if (s->fs1gp && !(vtd->cap_reg & VTD_CAP_FS1GP)) {
>> + error_setg(errp, "Stage-1 1GB huge page is unsupported by host
>> IOMMU");
>> + return false;
>> + }
>> +#endif
>> +
>> error_setg(errp, "host device is uncompatible with stage-1
>> translation");
>> return false;
>> }
