Re: testing mca/init patch

[david mosberger <dmosberger@gmail.com>]

Keith,

On 8/31/05, Keith Owens <kaos@sgi.com> wrote:
> On Wed, 31 Aug 2005 21:58:58 -0700,
> david mosberger <dmosberger@gmail.com> wrote:

> >- In several places there are checks of the form:
> >
> >+ if ((r12 & -KERNEL_STACK_SIZE) != r13) {
> >
> >  I don't understand why you're doing this.  You should check for (r12
> >- r13) <  KERNEL_STACK_SIZE.  That does the same without relying on
> >alignments (which is something we have been careful to avoid in all
> >other ia64 code).  This should also let you drop the patch to
> >vmlinux.lds.S.
> 
> Paranoia.  I have seen several MCA/INIT events fail because they were
> delivered while the cpu was in PAL/SAL.  r12 and r13 are preserved
> around calls to PAL/SAL, but they are not preserved _within_ PAL/SAL.
> I am trying to verify as much as possible of the original stack before
> updating it, the alignment check is something useful that I can test
> for.

I'm not suggesting to get rid of the test completely, I suggesting to
replace it with a range check of the form:

   (r12 - r13) <  KERNEL_STACK_SIZE

that should be about as tight a check as the original without making
alignment-assumptions.

  --david

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