Re: [Xen-devel] [PATCH] public: there's no MMUEXT_SET_FOREIGNDOM

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.06.17 at 14:29, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 08/06/17 16:19, Jan Beulich wrote:
>> Correct respective comments.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
>> ---
>> 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.
> 
> Nothing actually uses the clear/copy subops, as far as I can tell,

The 32-bit XenoLinux (at least our forward port) has been using
them for certain highmem accesses.

> although they could actually be used for a minor performance
> optimisation for HVM domain builder domains, to avoid HAP mutations. 
> I'd agree with restricting them to RAM only.

Okay.

Jan


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