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From: Ingo Molnar <mingo@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: X86 ML <x86@kernel.org>, Andy Lutomirski <luto@amacapital.net>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 15/15] x86/lib/memcpy_64.S: Convert memcpy to ALTERNATIVE_2 macro
Date: Thu, 5 Mar 2015 01:26:40 +0100	[thread overview]
Message-ID: <20150305002640.GA20449@gmail.com> (raw)
In-Reply-To: <20150304135853.GF3516@pd.tnic>


* Borislav Petkov <bp@alien8.de> wrote:

> On Wed, Mar 04, 2015 at 08:26:33AM +0100, Ingo Molnar wrote:
> > Since most CPUs we care about have ERMS, wouldn't it be better to
> > patch in the actual memcpy_erms sequence into the primary memcpy()
> > function? It's just about 9 bytes AFAICT.
> 
> Actually, most set REP_GOOD - all Intel family 6 and all relevant 
> AMDs.
> 
> And only the newer Intels have ERMS. My SNB, for example doesn't 
> while IVB has it. So I'd guess everything >= IVB would have it.

Well, my point equally applies to all variants: it's better to avoid 
the NOP or JMP overhead (however small it may be), by simply copying 
the ideal memcpy routine into memcpy()?

I.e. while I'd not want to patch in memcpy_orig (it's legacy really), 
but the other two variants, ERMS and REP MOVSQ could be patched in 
directly via ALTERNATIVE_2()?

Thanks,

	Ingo

  reply	other threads:[~2015-03-05  0:26 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-24 11:14 [PATCH v2 00/15] x86, alternatives: Instruction padding and more robust JMPs Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 01/15] x86/lib/copy_user_64.S: Remove FIX_ALIGNMENT define Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 02/15] x86/alternatives: Cleanup DPRINTK macro Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 03/15] x86/alternatives: Add instruction padding Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 04/15] x86/alternatives: Make JMPs more robust Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 05/15] x86/alternatives: Use optimized NOPs for padding Borislav Petkov
2015-03-04  6:43   ` Ingo Molnar
2015-03-04  8:42     ` Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 06/15] x86/lib/copy_page_64.S: Use generic ALTERNATIVE macro Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 07/15] x86/lib/copy_user_64.S: Convert to ALTERNATIVE_2 Borislav Petkov
2015-03-04  6:25   ` Ingo Molnar
2015-03-04  7:13     ` Ingo Molnar
2015-03-04  9:06       ` Borislav Petkov
2015-03-05  0:34         ` Ingo Molnar
2015-03-05  8:23           ` Borislav Petkov
2015-03-04  9:00     ` Borislav Petkov
2015-03-05  0:32       ` Ingo Molnar
2015-03-05  8:35         ` Borislav Petkov
2015-03-05  9:34           ` Ingo Molnar
2015-03-05  9:46             ` Ingo Molnar
2015-02-24 11:14 ` [PATCH v2 08/15] x86/smap: Use ALTERNATIVE macro Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 09/15] x86/entry_32: Convert X86_INVD_BUG to " Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 10/15] x86/lib/clear_page_64.S: Convert to ALTERNATIVE_2 macro Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 11/15] x86/asm: Use alternative_2() in rdtsc_barrier() Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 12/15] x86/asm: Cleanup prefetch primitives Borislav Petkov
2015-03-04  6:48   ` Ingo Molnar
2015-03-04  9:08     ` Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 13/15] x86/lib/memset_64.S: Convert to ALTERNATIVE_2 macro Borislav Petkov
2015-02-24 11:14 ` [PATCH v2 14/15] x86/lib/memmove_64.S: Convert memmove() to ALTERNATIVE macro Borislav Petkov
2015-03-04  7:19   ` Ingo Molnar
2015-02-24 11:14 ` [PATCH v2 15/15] x86/lib/memcpy_64.S: Convert memcpy to ALTERNATIVE_2 macro Borislav Petkov
2015-03-04  7:26   ` Ingo Molnar
2015-03-04 13:58     ` Borislav Petkov
2015-03-05  0:26       ` Ingo Molnar [this message]
2015-03-05  8:37         ` Borislav Petkov
2015-02-24 20:25 ` [PATCH v2 00/15] x86, alternatives: Instruction padding and more robust JMPs Andy Lutomirski
2015-02-26 18:13 ` Borislav Petkov
2015-02-26 18:16   ` [PATCH 1/3] perf/bench: Fix mem* routines usage after alternatives change Borislav Petkov
2015-02-26 18:16     ` [PATCH 2/3] perf/bench: Carve out mem routine benchmarking Borislav Petkov
2015-02-26 18:16     ` [PATCH 3/3] perf/bench: Add -r all so that you can run all mem* routines Borislav Petkov
2015-03-04  7:30       ` Ingo Molnar
2015-03-02 14:51   ` [PATCH v2 00/15] x86, alternatives: Instruction padding and more robust JMPs Hitoshi Mitake
2015-03-02 16:27     ` Borislav Petkov
  -- strict thread matches above, loose matches on Subject: below --
2015-03-27 14:58 [PATCH v2 15/15] x86/lib/memcpy_64.S: Convert memcpy to ALTERNATIVE_2 macro David Laight

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