Re: [Xen-devel] [PATCH v3] x86/p2m: use large pages for MMIO mappings

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.01.16 at 17:32, <ian.campbell@xxxxxxxxxx> wrote:
> I must confess I'm not entirely following what the various proposals are,

What is currently implemented by the patch is that, upon error on
iteration N the hypervisor would clean up on a best effort basis and
return the error indicator. In the alternative suggested model it
wouldn't do any cleanup and return N to indicate how far success
was seen; only in the event that N=0 would an error code be
returned.

> but FWIW I have no in-principal problem with the caller (by which I think
> you mean the tools?)

Yes.

> having to cleanup partial success in order to allow
> incremental attempts to set things up with smaller and smaller page sizes.

Except that in the new x86 model we're not talking about decreasing
page size, but just the splitting the hypervisor does in place of true
preemption. Decreasing page size would actually be harmful to the
goal of using large pages for the mappings.

Jan


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