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x86: Side-step lguest problem by only building cmpxchg8b_emu for pre-Pentium 

Commit 79e1dd05d1 "x86: Provide an alternative() based
cmpxchg64()" broke lguest, even on systems which have cmpxchg8b
support.  The emulation code gets used until alternatives get
run, but it contains native instructions, not their paravirt
alternatives.

The simplest fix is to turn this code off except for 386 and 486
builds.

Reported-by: Johannes Stezenbach <js@sig21.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: lguest@ozlabs.org
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <200910261426.05769.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
hifive-unleashed-5.1
Rusty Russell 2009-10-26 14:26:04 +10:30 committed by Ingo Molnar
parent 14a3f40aaf
commit ae1b22f6e4
1 changed files with 1 additions and 1 deletions
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arch/x86/Kconfig.cpu
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@ -400,7 +400,7 @@ config X86_TSC
config X86_CMPXCHG64
def_bool y
depends on X86_PAE || X86_64 || MCORE2 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MATOM
depends on !M386 && !M486
# this should be set for all -march=.. options where the compiler
# generates cmov.