Re: [Xen-ia64-devel] GET_THIS_PADDR appears to be broken

[Horms <horms@xxxxxxxxxxxx>]

On Wed, Jun 27, 2007 at 02:19:20PM +0200, tgingold@xxxxxxx wrote:
> Quoting Horms <horms@xxxxxxxxxxxx>:
> 
> > GET_THIS_PADDR() doesn't appear to work correclty
> > on xen-ia64-unstable.hg 15165:96331db61e47
> >
> > Long-winded description of why
> >
> >   cpu_data           = 0xf000000004410000
> >   ia64_tpa(cpu_data) = 0x0000000004410000
> >   __per_cpu_start    = 0x0003ffffffff0000
> >
> >   ia64_set_kr(IA64_KR_PER_CPU_DATA,
> >               ia64_tpa(cpu_data) - (long) __per_cpu_start);
> >   ar.k3              = ia64_tpa(cpu_data) - __per_cpu_start;
> >                      = 0x0000000004410000 - 0xf000000004410000
> >                    = 0x0f00000004420000 # N.B Underflow
> 
> I am lost here :-(  I though ar.kX were reserved by the domains.

I think that is true too.

If my reading of cpu_init() is correct then kX get saved into the
per_cpu variable cpu_kr, which is an array. However it did seem that the
k3 value was sane when I ran my test - no domU present.

However, the question does arise, if kX are unavailable,
then how does assembly code access the physical address of
a per_cpu variable, as if k3 is stashed in a per_cpu variable
there is a circular dependancy.

> 
> ...
> > Solution 1
> ...
> /home/horms/work/xen/xen-ia64-unstable.hg/xen/arch/ia64/linux-xen/mca_asm.S:271:
> > relocation truncated to fit: IMM22 against symbol
> > `per_cpu__ia64_mca_pal_base' defined in .data.percpu section in
> > /home/horms/work/xen/xen-ia64-unstable.hg/xen/arch/ia64/built_in.o
> >
> > I'm not really sure what that means, other than that
> > per_cpu__ia64_mca_pal_base aka THIS_CPU(ia64_mca_pal_base)
> > ought to be a 22bit integer, which it isn't.
> 
> This is the right reason.
> 
> > I also noticed that the assembled code on xen and linux differ.
> Hue, there are data not code!
> 
> Tristan.

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/


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