Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

[H. Peter Anvin]

Ingo Molnar wrote:
> * Klaus S. Madsen <ksm@xxxxxxxxxxxxxxxx> wrote:
>
> > The following patch solves the segfault, by changing the mmap flags of 
> > the video memory area, to allow execution. The patch is against 
> > libx86-0.99 available from http://www.codon.org.uk/~mjg59/libx86/
> >
> > --- libx86-0.99/x86-common.c	2006-09-08 00:44:27.000000000 +0200
> > +++ libx86-0.99.new/x86-common.c	2008-03-01 10:08:25.000000000 +0100
> > @@ -232,7 +232,7 @@
> >  	}
> >  
> >  	m = mmap((void *)0xa0000, 0x100000 - 0xa0000,
> > -	 PROT_READ | PROT_WRITE,
> > +	 PROT_READ | PROT_WRITE | PROT_EXEC,
>
> are you sure you ID-ed the right commit that broke things?
>
> while requiring PROT_EXEC is fine, breaking existing user-space apps 
> over that is not fine. So are you absolutely sure that by reverting that 
> PWT|PCD commit, s2ram again starts to work? That's utmost weird...
>
> perhaps there's some CPU bug that causes NX to _NOT_ work if only PCD is 
> used (not PCD|PWT). Seems like a pretty unlikely scenario though.

It really does.  What would be much more likely is that the PCD -> 
(PCD|PWT) triggered something in the kernel proper.

	-hpa
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