Re: [Qemu-devel] [PATCH v3 09/12] intel_iommu: allow dev-iotlb context entry conditionally

[Jason Wang]

On 2017年05月10日 16:01, Peter Xu wrote:
> When device-iotlb is not specified, we should fail this check.
>
> Signed-off-by: Peter Xu <address@hidden>
> ---
>   hw/i386/intel_iommu.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 05ae631..1a7eba2 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -836,6 +836,8 @@ static int vtd_dev_to_context_entry(IntelIOMMUState *s, 
> uint8_t bus_num,
>   {
>       VTDRootEntry re;
>       int ret_fr;
> +    bool type_fail = false;
> +    X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
>   
>       ret_fr = vtd_get_root_entry(s, bus_num, &re);
>       if (ret_fr) {
> @@ -872,10 +874,19 @@ static int vtd_dev_to_context_entry(IntelIOMMUState *s, 
> uint8_t bus_num,
>       } else {
>           switch (vtd_ce_get_type(ce)) {
>           case VTD_CONTEXT_TT_MULTI_LEVEL:
> -            /* fall through */
> +            /* Always supported */
> +            break;
>           case VTD_CONTEXT_TT_DEV_IOTLB:
> +            if (!x86_iommu->dt_supported) {
> +                type_fail = true;
> +            }
>               break;
>           default:
> +            /* Unknwon type */
> +            type_fail = true;
> +            break;
> +        }
> +        if (type_fail) {
>               trace_vtd_ce_invalid(ce->hi, ce->lo);
>               return -VTD_FR_CONTEXT_ENTRY_INV;
>           }

How about e.g exclude the type if not supported in vtd_ce_get_type()? 
This looks better than using something like type_fail.

Thanks