Re: [Xen-devel] [RFC PATCH 1/2] xen: introduce arch_iommu_grant_(un)map_page

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-07-08 at 16:53 +0100, Stefano Stabellini wrote:
> +int arch_iommu_grant_map_page(struct domain *d, unsigned long frame,
> +                              unsigned flags)
> +{
> +    p2m_type_t t;
> +
> +    /* Grant mappings can be used for DMA requests. The dev_bus_addr 
> returned by
> +     * the hypercall is the MFN (not the IPA). For device protected by
> +     * an IOMMU, Xen needs to add a 1:1 mapping in the domain p2m to
> +     * allow DMA request to work.
> +     * This is only valid when the domain is directed mapped.
> +     */
> +    BUG_ON(!is_domain_direct_mapped(d));

What stops a non-1:1 guest from trying to map a grant reference and
ending up here?

Ian.


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