Re: [PATCH] x86: make clflush a required feature on x86_64

From: H. Peter Anvin
Date: Fri Jan 18 2008 - 00:11:13 EST


Kyle McMartin wrote:
Hopefully nobody will be stupid enough to implement a cpu without
it. Frankly, it seems safe enough given we already require SSE2.

This means the compiler can optimise away "if (!cpu_has_clflush)"
blocks.

Signed-off-by: Kyle McMartin <kyle@xxxxxxxxxxx>
---
include/asm-x86/cpufeature_64.h | 3 +++
include/asm-x86/required-features.h | 4 +++-
2 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/include/asm-x86/cpufeature_64.h b/include/asm-x86/cpufeature_64.h
index e18496b..ef11d27 100644
--- a/include/asm-x86/cpufeature_64.h
+++ b/include/asm-x86/cpufeature_64.h
@@ -18,6 +18,9 @@
#undef cpu_has_mp
#define cpu_has_mp 1 /* XXX */
+#undef cpu_has_clflush
+#define cpu_has_clflush 1
+
#undef cpu_has_k6_mtrr
#define cpu_has_k6_mtrr 0

Unnecessary. These overrides are only needed for the anticases (known to be zero) or for some special hacks.

Stuff that have proper CPUID bits get these defined as constants via the REQUIRED_MASK macros.

-hpa
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