Messages in this thread | | | Date | Wed, 15 Jul 2015 19:39:26 -0700 | Subject | Re: [REGRESSION] 4.2-rc2: early boot memory corruption from FPU rework | From | Linus Torvalds <> |
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On Wed, Jul 15, 2015 at 5:34 PM, Dave Hansen <dave.hansen@linux.intel.com> wrote: > > The old code sized the buffer in a fully architectural way and it > worked. The CPU *tells* you how much memory the 'xsave' instruction is > going to scribble on. The new code just merrily calls it and let it > scribble away. This is as clear-cut a regression as I've ever seen.
Yes, I think we'll need to revert it, or do something else drastic like make that initial fp state allocation *much* bigger and then have a "disable xsaves if if it's still not big enough".
setup_xstate_features() should be able to easily just say "this was the maximum offset+size we saw", and we can take that to either do a proper allocation, or verify that the static allocation is indeed big enough.
Apparently a straight revert doesn't work, if only because things in that area have been renamed very aggressively (both files and functions and variables). Ingo?
Linus
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