Re: [Xen-devel] [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.07.14 at 03:36, <tiejun.chen@xxxxxxxxx> wrote:
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -1867,8 +1867,14 @@ static int rmrr_identity_mapping(struct domain *d,
>  
>      while ( base_pfn < end_pfn )
>      {
> -        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
> -                                  IOMMUF_readable|IOMMUF_writable) )
> +        if ( iommu_use_hap_pt(d) )
> +        {
> +            ASSERT(!iommu_passthrough || !is_hardware_domain(d));
> +            if ( set_identity_p2m_entry(d, base_pfn) )
> +                return -1;
> +        }
> +        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
> +                                       IOMMUF_readable|IOMMUF_writable) )
>              return -1;
>          base_pfn++;
>      }

So I wonder how this plays together with

    /* FIXME: Because USB RMRR conflicts with guest bios region,
     * ignore USB RMRR temporarily.
     */
    seg = pdev->seg;
    bus = pdev->bus;
    if ( is_usb_device(seg, bus, pdev->devfn) )
    {
        ret = 0;
        goto done;
    }

later in the same file (in intel_iommu_assign_device()). I.e. the
improvement you claim won't be achieved for passed through USB
devices afaict. One more aspect supporting my view that this
needs fully addressing rather than any such partial solution.

Jan


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