linux-kernel - Re: [RFC -tip] x86,apic -- reduce disable

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]

Date:	Sun, 05 Jul 2009 12:18:00 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC -tip] x86,apic -- reduce disable_apic usage

Cyrill Gorcunov wrote:
> 
> Peter, Maciej but how kernel behaved on older cpu long time ago?
> 
> I mean -- should user pass "lapic" cmdline option too be
> able to use apic functionality? (i'm asking since I just
> don't know how it had been working before). Current
> code (if only I'm not _missing_ something) relies on cpu_has_apic
> bit. And even if MP table has been parsed and APIC base found,
> cpu_has_apic could be not set so detect_init_APIC will fail
> if no "lapic" option passed (in case of old cpu without this cpuid
> bit produced) as we eventually stay with pic mode.
> 

Well, systems with discrete APICs were few and far between.  I'm not
sure if there are any such systems still in meaningful existence (kind
of like Voyager.)  That makes it a bit hard to test things, and
certainly means we shouldn't bend over backwards in doing *anything*
that could possibly break other machines.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
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/