From: Borislav Petkov <bp@alien8.de>
To: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Mario Gzuk <mariogzuk@technikz.de>
Subject: Re: [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of no CPUID
Date: Wed, 28 Nov 2012 21:41:58 +0100 [thread overview]
Message-ID: <20121128204158.GC14635@liondog.tnic> (raw)
In-Reply-To: <1354132230-21854-9-git-send-email-hpa@linux.intel.com>
On Wed, Nov 28, 2012 at 11:50:30AM -0800, H. Peter Anvin wrote:
> From: "H. Peter Anvin" <hpa@linux.intel.com>
>
> Simplify the implementation of sync_core() for the case where we may
> not have the CPUID instruction available.
>
> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
> ---
> arch/x86/include/asm/processor.h | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 9a4ee46..b381df7 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -673,17 +673,24 @@ static inline void sync_core(void)
> int tmp;
>
> #ifdef CONFIG_M486
> - if (boot_cpu_data.x86 < 5)
> - /* There is no speculative execution.
> - * jmp is a barrier to prefetching. */
> - asm volatile("jmp 1f\n1:\n" ::: "memory");
> - else
> + /*
> + * Do a CPUID if available, otherwise do a jump. The jump
> + * can conveniently enough be the jump around CPUID.
> + */
> + asm volatile("cmpl %2,%1\n\t"
> + "jl 1f\n\t"
> + "cpuid\n"
> + "1:"
> + : "=a" (tmp)
> + : "rm" (boot_cpu_data.cpuid_level), "ri" (0), "0" (1)
> + : "ebx", "ecx", "edx", "memory");
> +#else
> + /* cpuid is a barrier to speculative execution.
> + * Prefetched instructions are automatically
> + * invalidated when modified. */
While at it, you could correct this comment to adhere to kernel coding
style:
/*
* cpuid is a barrier...
* ...
*/
> + asm volatile("cpuid" : "=a" (tmp) : "0" (1)
> + : "ebx", "ecx", "edx", "memory");
... and then write this in its shorter form:
tmp = cpuid_eax(1);
to have it a bit easier on the eyes.
Thanks.
--
Regards/Gruss,
Boris.
next prev parent reply other threads:[~2012-11-28 20:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-28 19:50 [PATCH 0/8] RFC: Remove 386 support H. Peter Anvin
2012-11-28 19:50 ` [PATCH 1/8] x86, 386 removal: Remove CONFIG_M386 from Kconfig H. Peter Anvin
2012-12-01 0:34 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 2/8] x86, 386 removal: Remove CONFIG_CMPXCHG H. Peter Anvin
2012-12-01 0:35 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 3/8] x86, 386 removal: Remove CONFIG_XADD H. Peter Anvin
2012-11-28 20:30 ` Borislav Petkov
2012-12-01 0:36 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 4/8] x86, 386 removal: Remove CONFIG_BSWAP H. Peter Anvin
2012-12-01 0:37 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 5/8] x86, 386 removal: Remove CONFIG_INVLPG H. Peter Anvin
2012-12-01 0:38 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 6/8] x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK H. Peter Anvin
2012-11-28 20:52 ` Alan Cox
2012-11-28 23:11 ` H. Peter Anvin
2012-12-01 0:42 ` [tip:x86/nuke386] x86, 386 removal: Document Nx586 as a 386 and thus unsupported tip-bot for H. Peter Anvin
2012-12-01 0:39 ` [tip:x86/nuke386] x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 7/8] x86, 386 removal: Remove CONFIG_X86_POPAD_OK H. Peter Anvin
2012-12-01 0:40 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
2012-11-28 19:50 ` [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of no CPUID H. Peter Anvin
2012-11-28 20:41 ` Borislav Petkov [this message]
2012-11-29 0:14 ` H. Peter Anvin
2012-11-29 9:13 ` Borislav Petkov
2012-11-29 21:06 ` H. Peter Anvin
2012-11-29 21:18 ` Borislav Petkov
2012-11-29 21:20 ` H. Peter Anvin
2012-11-29 21:31 ` Borislav Petkov
2012-11-29 21:24 ` H. Peter Anvin
2012-11-29 21:34 ` Borislav Petkov
2012-11-30 17:01 ` Linus Torvalds
2012-11-30 17:28 ` Borislav Petkov
2012-11-30 18:03 ` H. Peter Anvin
2012-11-30 18:10 ` Borislav Petkov
2012-11-30 18:40 ` H. Peter Anvin
2012-12-01 0:41 ` [tip:x86/nuke386] " tip-bot for H. Peter Anvin
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