Re: [PATCH] public: there's no MMUEXT_SET_FOREIGNDOM

[Julien Grall <julien.grall@arm.com>]

Hi Jan,

On 08/06/17 16:19, Jan Beulich wrote:
> Correct respective comments.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> MMUEXT_{CLEAR,COPY}_PAGE in fact also allow to be invoked on DOMID_IO
> owned pages at present. I've intentionally not added this to the text,
> as I'm not sure we really mean to allow this. If we do, I think the
> operation should also be allowed for MMIO pages not happening to have
> an associated struct page_info.
>
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -550,16 +550,19 @@ DEFINE_XEN_GUEST_HANDLE(mmuext_op_t);
>   * is useful to ensure that no mappings to the OS's own heap are accidentally
>   * installed. (e.g., in Linux this could cause havoc as reference counts
>   * aren't adjusted on the I/O-mapping code path).
> - * This only makes sense in MMUEXT_SET_FOREIGNDOM, but in that context can
> - * be specified by any calling domain.
> + * This only makes sense as HYPERVISOR_mmu_update()'s and
> + * HYPERVISOR_update_va_mapping_otherdomain()'s "foreigndom" argument. For
> + * HYPERVISOR_mmu_update() context it can be specified by any calling domain,
> + * otherwise it's only permitted if the caller is privileged.
>   */
>  #define DOMID_IO             xen_mk_uint(0x7FF1)
>
>  /*
>   * DOMID_XEN is used to allow privileged domains to map restricted parts of
>   * Xen's heap space (e.g., the machine_to_phys table).
> - * This only makes sense in MMUEXT_SET_FOREIGNDOM, and is only permitted if
> - * the caller is privileged.
> + * This only makes sense as HYPERVISOR_mmu_update()'s, HYPERVISOR_mmuext_op()'s,
> + * or HYPERVISOR_update_va_mapping_otherdomain()'s "foreigndom" argument, and is
> + * only permitted if the caller is privileged.

DOMID_XEN is used on ARM for mapping Xen buffer (e.g trace) using 
physmap hypercall with XENMAPSPACE_foreign_gmfn_foreign.


>   */
>  #define DOMID_XEN            xen_mk_uint(0x7FF2)

Cheers,

-- 
Julien Grall

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