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
| ||
|
Date: Sat, 25 Apr 2015 04:17:04 +0200 From: Denys Vlasenko <vda.linux@...glemail.com> To: Andy Lutomirski <luto@...capital.net> Cc: Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>, Linus Torvalds <torvalds@...ux-foundation.org>, 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> Subject: Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue On Fri, Apr 24, 2015 at 10:50 PM, Andy Lutomirski <luto@...capital.net> wrote: > On Fri, Apr 24, 2015 at 1:46 PM, Denys Vlasenko >>> This might be way more trouble than it's worth. >> >> Exactly my feeling. What are you trying to save? About four CPU >> cycles of checking %ss != __KERNEL_DS on each switch_to? >> That's not worth bothering about. Your last patch seems to be perfect. > > We'll have to do the write to ss almost every time an AMD CPU sleeps > in a syscall. Why do you think so? Scheduling from a syscall which decided to block won't require writing to %ss, since in this case %ss isn't NULL. Writing to %ss will happen every time we schedule from an interrupt. With timer interrupt every 1 ms it means scheduling at most ~1000 times per second, if _every_ such interrupt causes task switch. This is still not often enough to worry. -- 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/
Powered by blists - more mailing lists