Re: [Xen-devel] ARM: grant table setup

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-04-22 at 10:37 -0700, Jonathan Daugherty wrote:
> Hi,
> 
> I'm modifying FreeRTOS to run as a Xen guest and I'm working on grant
> table setup.  The documentation for the Xen ARM ABI states:
> 
>   The grant table is mapped using the HYPERVISOR_memory_op sub-op
>   XENMEM_add_to_physmap, passing XENMAPSPACE_grant_table as space
>   parameter. The memory range specified under the Xen compatible
>   hypervisor node on device tree can be used as target gpfn for the
>   mapping.
> 
> However, I noticed that there is also the GNTTABOP_setup_table
> operation.  The two seem to overlap in things they do (such as growing
> the grant table if the request requires it).  Linux appears to use the
> physmap operation for ARM ("hvm") guests and setup_table otherwise.

I think Linux uses the physmap interface for x86 HVM and PVH guests too.

> However, early on my implementation called setup_table to very strange
> effect (bogus MFNs in the frame_list). Provided that is indeed
> inappropriate, would it be reasonable to make setup_table return a
> failure status if called for HVM domains?

I think that would make sense, but the correct condition would probably
be autotranslated guests rather than hvm.

Ian.


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