Re: [Xen-devel] [PATCH V2 10/25] tools/libxl: create vIOMMU during domain construction

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Aug 09, 2017 at 04:34:11PM -0400, Lan Tianyu wrote:
> From: Chao Gao <chao.gao@xxxxxxxxx>
> 
> If guest is configured to have a vIOMMU, create it during domain construction.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> ---
>  tools/libxl/libxl_x86.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
> index 455f6f0..ace20e5 100644
> --- a/tools/libxl/libxl_x86.c
> +++ b/tools/libxl/libxl_x86.c
> @@ -341,8 +341,36 @@ int libxl__arch_domain_create(libxl__gc *gc, 
> libxl_domain_config *d_config,
>      if (d_config->b_info.type == LIBXL_DOMAIN_TYPE_HVM) {

I would rather change this check so it's:

d_config->b_info.type != LIBXL_DOMAIN_TYPE_PV

Is there any reason why PVH guests shouldn't get a vIOMMU?

>          unsigned long shadow = DIV_ROUNDUP(d_config->b_info.shadow_memkb,
>                                             1024);
> +        libxl_viommu_info *viommu = &d_config->b_info.viommu;
> +
>          xc_shadow_control(ctx->xch, domid, 
> XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION,
>                            NULL, 0, &shadow, 0, NULL);
> +
> +        /* Check supported capbilities and create viommu */
> +        if (viommu->type) {
> +            uint32_t id;
> +            uint64_t cap;
> +
> +            if (xc_viommu_query_cap(ctx->xch, domid, viommu->type, &cap)) {
> +                LOGED(ERROR, domid, "failed to query vIOMMU's capabilities");
> +                ret = ERROR_FAIL;
> +                goto out;
> +            }
> +
> +            if ((cap & viommu->cap) != viommu->cap) {
> +                LOGED(ERROR, domid, "vIOMMU: Unsupported cap %"PRIu64, cap);
> +                ret = ERROR_FAIL;
> +                goto out;
> +            }

As said earlier, I don't think you should check the capabilities, just
try to create the vIOMMU and if the selected capabilities are not
supported xc_viommu_create should fail.

Roger.

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