linux-kernel - Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue

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Message-ID: <20150501090353.GA10239@pd.tnic>
Date:	Fri, 1 May 2015 11:03:53 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.com>
Subject: Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor
 attribute issue

On Thu, Apr 30, 2015 at 04:23:26PM -0700, H. Peter Anvin wrote:
> I probably should have added that the microbenchmark specifically tests
> for an atomic 5-byte NOP (as required by tracepoints etc.)  If the
> requirement for 5-byte atomic is dropped there might be faster
> combinations, e.g. 66 66 66 90 might work better on some platforms, or
> using very long 0F 1F sequences.

Right, so I was thinking of extending it for all sizes 1 - 15 and then
run it on boxes. I'll keep you posted.

Thanks for the toy - now I get to have some fun. :-)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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