linux-kernel - Re: Sysenter crash with Nested Task Bit set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20060918150650.GA10336@elte.hu>
Date:	Mon, 18 Sep 2006 17:06:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	Andrew Morton <akpm@...l.org>,
	Chuck Ebbert <76306.1226@...puserve.com>,
	In Cognito <defend.the.world@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>
Subject: Re: Sysenter crash with Nested Task Bit set


* Linus Torvalds <torvalds@...l.org> wrote:

> And sysenter really is very special because of the weak trap 
> semantics. Damn. We could either fix it in the sysenter code-path, or 
> in the task-switch one, and both of them are timing-critical, but task 
> switching perhaps just a tad less so.

agreed. Context-switching is 10 times less frequent on most workloads 
than syscalls, so if it takes 10 cycles in the context-switch path to 
eliminate a 1 cycle overhead in the syscall-entry path then we are still 
break-even on average. In this case the overhead is similar i think, so 
the switch_to() fix is preferable.

	Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/