Re: [PATCH v2 3/4] xen/arm: clean and invalidate all guest caches by VMID after domain build.

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 05/02/14 16:03, Ian Campbell wrote:
> Guests are initially started with caches disabled and so we need to make sure
> they see consistent data in RAM (requiring a cache clean) but also that they
> do not have old stale data suddenly appear in the caches when they enable
> their caches (requiring the invalidate).
>
> This can be split into two halves. First we must flush each page as it is
> allocated to the guest. It is not sufficient to do the flush at scrub time
> since this will miss pages which are ballooned out by the guest (where the
> guest must scrub if it cares about not leaking the pagecontent). We need to
> clean as well as invalidate to make sure that any scrubbing which has occured
> gets committed to real RAM. To achieve this add a new cacheflush_page function,
> which is a stub on x86.
>
> Secondly we need to flush anything which the domain builder touches, which we
> do via a new domctl.

As I understand, there is no hypercall continuation so if a domain give 
a big range Xen will get stuck for a long time (no softirq will be 
handled on the current processor ...). Shall we at least use 
hypercall_create_continuation?

-- 
Julien Grall