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x86: disable static NOPLs on 32 bits 

On 32-bit, at least the generic nops are fairly reasonable, but the
default nops for 64-bit really look pretty sad, and the P6 nops really do
look better.

So I would suggest perhaps moving the static P6 nop selection into the
CONFIG_X86_64 thing.

The alternative is to just get rid of that static nop selection, and just
have two cases: 32-bit and 64-bit, and just pick obviously safe cases for
them.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Linus Torvalds 2008-09-05 09:30:14 -07:00 committed by H. Peter Anvin
parent 0253398ca1
commit 14469a8dd2
1 changed files with 8 additions and 5 deletions
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13
arch/x86/Kconfig.cpu
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@ -382,14 +382,17 @@ config X86_OOSTORE
# P6_NOPs are a relatively minor optimization that require a family >= # P6_NOPs are a relatively minor optimization that require a family >=
# 6 processor, except that it is broken on certain VIA chips. # 6 processor, except that it is broken on certain VIA chips.
# Furthermore, AMD chips prefer a totally different sequence of NOPs # Furthermore, AMD chips prefer a totally different sequence of NOPs
# (which work on all CPUs). As a result, disallow these if we're # (which work on all CPUs). In addition, it looks like Virtual PC
# compiling X86_GENERIC but not X86_64 (these NOPs do work on all # does not understand them.
# x86-64 capable chips); the list of processors in the right-hand clause #
# are the cores that benefit from this optimization. # As a result, disallow these if we're not compiling for X86_64 (these
# NOPs do work on all x86-64 capable chips); the list of processors in
# the right-hand clause are the cores that benefit from this optimization.
# #
config X86_P6_NOP config X86_P6_NOP
def_bool y def_bool y
depends on (X86_64 || !X86_GENERIC) && (M686 || MPENTIUMII || MPENTIUMIII || MPENTIUMM || MCORE2 || MPENTIUM4 || MPSC) depends on X86_64
depends on (MCORE2 || MPENTIUM4 || MPSC)
config X86_TSC config X86_TSC
def_bool y def_bool y