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SubjectRE: [PATCH 3/6] x86: Add support for the clwb instruction
Date
No, it doesn't.  x86 requires 3.4+ at a minimum.

________________________________
From: Borislav Petkov
Sent: Wednesday, November 12, 2014 4:39:09 AM
To: Ross Zwisler
Cc: linux-kernel@vger.kernel.org; Anvin, H Peter; Ingo Molnar; Thomas Gleixner; David Airlie; dri-devel@lists.freedesktop.org; x86@kernel.org
Subject: Re: [PATCH 3/6] x86: Add support for the clwb instruction

On Tue, Nov 11, 2014 at 11:43:13AM -0700, Ross Zwisler wrote:
> +static inline void clwb(volatile void *__p)
> +{
> + alternative_io_2(".byte " __stringify(NOP_DS_PREFIX) "; clflush %P0",
> + ".byte 0x66; clflush %P0",
> + X86_FEATURE_CLFLUSHOPT,
> + ".byte 0x66; xsaveopt %P0",

Btw, I'm afraid you're going to have to spell out those new instruction
mnemonics as they aren't supported by older compilers:

CC drivers/gpu/drm/drm_cache.o
{standard input}: Assembler messages:
{standard input}:63: Error: no such instruction: `xsaveopt (%rax)'
{standard input}:249: Error: no such instruction: `xsaveopt (%rdi)'
{standard input}:283: Error: no such instruction: `xsaveopt -1(%rdx)'
make[1]: *** [drivers/gpu/drm/drm_cache.o] Error 1
make: *** [drivers/gpu/drm/drm_cache.o] Error 2
[boris@etch:14:35:40:k:14)-> gcc --version
gcc (GCC) 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

This is on a very old guest I have which has this gcc in it and the
kernel supports everything gcc >= 3.2.

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--


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