linux-kernel - Re: [PATCH 01/14] Introduce cpu_enabled

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: <20080715184822.GB29991@flint.arm.linux.org.uk>
Date:	Tue, 15 Jul 2008 19:48:22 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Alex Chiang <achiang@...com>, Andi Kleen <andi@...stfloor.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 01/14] Introduce cpu_enabled_map and friends

On Tue, Jul 15, 2008 at 12:16:32PM -0600, Matthew Wilcox wrote:
> On Tue, Jul 15, 2008 at 11:57:40AM -0600, Alex Chiang wrote:
> > My thought was that big SMP systems like ia64, possibly sparc and
> > ppc, and increasingly, x86, might find something like this
> > useful, as systems get larger and larger, and vendors are going
> > to want to do RAS-ish features, like the ability to keep CPUs in
> > firmware across reboots until told otherwise by the sysadmin.
> > 
> > Right now, a 'present' CPU strongly implies 'online' as well,
> > since we're calling cpu_up() for all 'present' CPUs in
> > smp_init(). But this hurts if:
> > 
> > 	- you don't actually want to bring up all 'present' CPUs
> > 	- you still want to interact with these weirdo zombie
> > 	  CPUs that are 'present' but not 'online'
> 
> Have you considered simply failing __cpu_up() for CPUs that are
> deconfigured by firmware?

But what if you want to have a system boot with, say, 4 CPUs and
then decide at run time to bring up another 4 CPUs when required?

How about having smp_init() call into arch code to query whether
it should bring up a not-already-online CPU?  Architectures that
want to do something special can then make the decision there and
everyone else can define the test completely away.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
--
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/