Xen devel - Feb 2006 - RE: Re: user/hypervisor address space solution

>From: Hollis Blanchard
>Sent: 2006年2月14日 19:13
>
>
>I don''t know what implications this could have for ia64, since they
suck
>in so much Linux code... but perhaps that Linux code isn''t the
stuff
>that deals with userland, so might not have uaccess users.
>[...]
Regarding this area to access domain parameters, IA64 should be OK since
xen/ia64 shares same virtual address space (i.e same ASN) with domain, thus able
to access pointer passed in directly. Linux style uaccess interfaces can easily
work for xen/ia64 in this aspect.

Thanks,
Kevin

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On Fri, 2006-02-17 at 17:05 +0800, Tian, Kevin wrote:
> 
> >From: Hollis Blanchard
> >Sent: 2006年2月14日 19:13
> >
> >I don''t know what implications this could have for ia64, since
they
> suck
> >in so much Linux code... but perhaps that Linux code isn''t the
stuff
> >that deals with userland, so might not have uaccess users.
> 
> Regarding this area to access domain parameters, IA64 should be OK
> since xen/ia64 shares same virtual address space (i.e same ASN) with
> domain, thus able to access pointer passed in directly. Linux style
> uaccess interfaces can easily work for xen/ia64 in this aspect.
Actually I was referring to the API rename, not the underlying
implementation. But since then I''ve changed my mind, and I''m
fine with
leaving e.g. "put_user" around, as long as nobody calls it from common
code. So if there are put_user() callers in the Linux code you suck in,
it will still be ok.

But while we''re on the subject, I recall hearing that IA64 has an issue
with TLB faults when accessing domain virtual addresses. Could you
elaborate on that? I guess you''re using a software-controlled TLB, and
when a fault occurs you need to call up to Linux to handle it?

-- 
Hollis Blanchard
IBM Linux Technology Center


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