Messages in this thread |  | | | Date | Mon, 3 Mar 2008 22:05:26 +0100 | | From | Pavel Machek <> | | Subject | Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending |
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Hi!
> However I wasn't able to make the problem go away, by removing the > _PAGE_PWT constants from __PAGE_KERNEL_NOCACHE and > __PAGE_KERNEL_VSYSCALL_NOCACHE in include-asm/pgtable.h in the newest > 2.6.25: > > diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h > index 174b877..f81c968 100644 > --- a/include/asm-x86/pgtable.h > +++ b/include/asm-x86/pgtable.h > @@ -84,9 +84,9 @@ extern pteval_t __PAGE_KERNEL, __PAGE_KERNEL_EXEC; > #define __PAGE_KERNEL_RO (__PAGE_KERNEL & ~_PAGE_RW) > #define __PAGE_KERNEL_RX (__PAGE_KERNEL_EXEC & ~_PAGE_RW) > #define __PAGE_KERNEL_EXEC_NOCACHE (__PAGE_KERNEL_EXEC | _PAGE_PCD | _PAGE_PWT) > -#define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD | _PAGE_PWT) > +#define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD) > #define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER) > -#define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD | _PAGE_PWT) > +#define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD) > #define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE) > #define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE) > > So while I'm fairly confident in that I bisected correctly, the number > of attempts I had to go through to get a reliable result, and the fact > that I cannot make the problem go away by reverting the current code to > something similar, counts quite a lot against me. > > However I'm 100% confident that the problem appears between > cf8fa920cb4271f17e0265c863d64bea1b31941a and > 925596a017bbd045ff711b778256f459e50a119, which is something like 16 > commits. I have been at both points in the tree at least 2 times, and > confirmed that cf8fa920cb4271f17e0265c863d64bea1b31941a worked for me, > and 925596a017bbd045ff711b778256f459e50a119 didn't. > > > 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... > I'm sure that it fixed the problem for me, yes, and I'm fairly confident > that I ran make clean && make to compile the kernel during the entire > bisection between the two commites mentioned above. > > > 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. > $ cat /proc/cpuinfo > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 15 > model name : Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz > stepping : 10 > > But I'm a bit puzzled by the fact that I'm aparently the only one how > have encountered the problem? Maybe it's only a problem if one also uses > PAE? (Thats just a wild guess to explain why I'm the only one seeing > this).
I do not have NX capable CPU in machine using for suspend testing. ... and you are using 32-bit userspace on 64-bit kernel, right?
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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