Re: [PATCH rfcv2 18/18] intel_iommu: Block migration if cap is updated

[Joao Martins <joao.m.martins@oracle.com>]

On 01/02/2024 07:28, Zhenzhong Duan wrote:
> When there is VFIO device and vIOMMU cap/ecap is updated based on host
> IOMMU cap/ecap, migration should be blocked.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>

Is this really needed considering migration with vIOMMU is already blocked anyways?

> ---
>  hw/i386/intel_iommu.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 72cc8b2c71..7f9ff653b2 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -39,6 +39,7 @@
>  #include "hw/i386/apic_internal.h"
>  #include "kvm/kvm_i386.h"
>  #include "migration/vmstate.h"
> +#include "migration/blocker.h"
>  #include "trace.h"
>  
>  #define S_AW_BITS (VTD_MGAW_FROM_CAP(s->cap) + 1)
> @@ -3829,6 +3830,8 @@ static int vtd_check_legacy_hdev(IntelIOMMUState *s,
>      return 0;
>  }
>  
> +static Error *vtd_mig_blocker;
> +
>  static int vtd_check_iommufd_hdev(IntelIOMMUState *s,
>                                    IOMMUFDDevice *idev,
>                                    Error **errp)
> @@ -3860,8 +3863,17 @@ static int vtd_check_iommufd_hdev(IntelIOMMUState *s,
>          tmp_cap |= VTD_CAP_MGAW(host_mgaw + 1);
>      }
>  
> -    s->cap = tmp_cap;
> -    return 0;
> +    if (s->cap != tmp_cap) {
> +        if (vtd_mig_blocker == NULL) {
> +            error_setg(&vtd_mig_blocker,
> +                       "cap/ecap update from host IOMMU block migration");
> +            ret = migrate_add_blocker(&vtd_mig_blocker, errp);
> +        }
> +        if (!ret) {
> +            s->cap = tmp_cap;
> +        }
> +    }
> +    return ret;
>  }
>  
>  static int vtd_check_hdev(IntelIOMMUState *s, VTDHostIOMMUDevice *vtd_hdev,