From: Andi Kleen <ak@suse.de>
To: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
Andi Kleen <ak@suse.de>, Andrew Morton <akpm@osdl.org>,
William Lee Irwin III <wli@holomorphy.com>,
"Raj, Ashok" <ashok.raj@intel.com>
Subject: Re: x86_64/HOTPLUG_CPU: NULL dereference doesn't #PF with init_level4_pgt
Date: Thu, 1 Dec 2005 14:18:57 +0100 [thread overview]
Message-ID: <20051201131857.GG19515@wotan.suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64.0511301859070.13220@montezuma.fsmlabs.com>
On Wed, Nov 30, 2005 at 08:03:33PM -0800, Zwane Mwaikambo wrote:
> NULL dereferences don't cause a page fault if the 4th level pagetable
> being used is init_level4_pgt because we never zap_low_mappings. Since
> the idle thread uses init_level4_pgt any bad dereferences happening there
> (e.g. from interrupts) won't cause a fault. Andi would you be fine with
> switching the idle threads to a different level4?
That recently changed. Are you sure it's still the case?
idle threads should always run with lazy TLB, no different mms.
That's important for performance.
If a NULL reference causes a oops or not depends on if user space
from the last process mapped a page to NULL or not.
-Andi
next prev parent reply other threads:[~2005-12-01 13:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-01 4:03 Zwane Mwaikambo
2005-12-01 13:18 ` Andi Kleen [this message]
2005-12-01 19:34 ` Zwane Mwaikambo
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