Re: [Xen-devel] [PATCH] x86: rework hypercall argument translation area setup

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 21/02/2013 12:26, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

>> Well, fine in principle. This manual setup/teardown of l2/l1 pagetables in
>> the perdomain area is getting a bit tiresome though isn't it? Isn't there
>> some setup helper that could be abstracted out for all users, and perhaps
>> even some automated teardown-and-freeing on domain destroy? I just sighed
>> when I saw more skanky pagetable manipulation for what is a conceptually
>> simple change.
> 
> I tried to spot pieces worth folding into helper functions, but
> didn't really find anything worthwhile (the purposes of the
> mappings are just too different). Perhaps we could have a
> map_pages_to_guest(), taking care of all intermediate page
> table levels? I can't see much else, and the main problem is that
> of tracking pages used for page tables here anyway.

Well, possibly even that might be an improvement.

> Are we concerned about the performance of guest GDT/LDT page
> (un)mappings?

LDT must often change on guest process context switch? So I would think yes
we do.

 -- Keir



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