Re: [Xen-devel] [PATCH] AMD-Vi: allocate root table on demand

[Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>]

Hi Jan,

Sorry for delay. Please seem my comment below.

On 3/3/17 21:29, Jan Beulich wrote:
> This was my originally intended fix for the AMD side of XSA-207:
> There's no need to unconditionally allocate the root table, and with
> that there's then also no way to leak it when a guest has no devices
> assigned.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/drivers/passthrough/amd/iommu_map.c
> +++ b/xen/drivers/passthrough/amd/iommu_map.c
> @@ -636,11 +636,10 @@ int amd_iommu_map_page(struct domain *d,
>  {
>      bool_t need_flush = 0;
>      struct domain_iommu *hd = dom_iommu(d);
> +    int rc;
>      unsigned long pt_mfn[7];
>      unsigned int merge_level;
>
> -    BUG_ON( !hd->arch.root_table );
> -
>      if ( iommu_use_hap_pt(d) )
>          return 0;
>
> @@ -648,6 +647,13 @@ int amd_iommu_map_page(struct domain *d,
>
>      spin_lock(&hd->arch.mapping_lock);
>
> +    rc = amd_iommu_alloc_root(hd);
> +    if ( rc )
> +    {
> +        spin_unlock(&hd->arch.mapping_lock);
> +        return rc;
Within function amd_iommu_map_page(), other failures seem to be
calling AMD_IOMMU_DEBUG() with error message, then calling domain_crash().
Wouldn't this also be needed for this case as the only error returned
is -ENOMEM.

Thanks,
Suravee

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