From: "Mika Penttilä" <mika.penttila@kolumbus.fi>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Petr Vandrovec <vandrove@vc.cvut.cz>,
Dave Jones <davej@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: EFAULT reading /dev/mem... - broken x86info
Date: Mon, 10 Nov 2003 21:36:53 +0200 [thread overview]
Message-ID: <3FAFE8D5.4020102@kolumbus.fi> (raw)
In-Reply-To: <3FAFDFFF.70100@colorfullife.com>
Manfred Spraul wrote:
> Petr Vandrovec wrote:
>
>> On Mon, Nov 10, 2003 at 06:17:37PM +0100, Manfred Spraul wrote:
>>
>>
>>> DEBUG_PAGEALLOC unmaps pages on kmem_cache_free and __free_pages().
>>> The pages are mapped again during get_free_pages and kmem_cache_alloc.
>>>
>>> 0x86000 looks like a normal page - what guarantees that it's not
>>> used by the kernel?
>>>
>>
>>
>> With DEBUG_PAGEALLOC there is no problem with page if it is USED by
>> the kernel.
>> Problem is if page is NOT USED - in this case kernel does not have it
>> in its
>> mapping, and bad thing happen.
>>
>>
> If the page is used by AGP, then it won't have a mapping either.
>
afaics, agp uses change_apge_attr() to turn on NOCACHE bit, and doesn't
remove the mapping.
--Mika
next prev parent reply other threads:[~2003-11-10 19:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-08 16:27 EFAULT reading /dev/mem... - broken x86info Petr Vandrovec
2003-11-10 13:55 ` Richard B. Johnson
2003-11-10 16:11 ` Dave Jones
2003-11-10 16:50 ` Manfred Spraul
2003-11-10 16:56 ` Dave Jones
2003-11-10 17:17 ` Manfred Spraul
2003-11-10 18:05 ` Petr Vandrovec
2003-11-10 18:59 ` Manfred Spraul
2003-11-10 19:36 ` Mika Penttilä [this message]
2003-11-10 19:47 ` Manfred Spraul
2003-11-10 20:24 ` Dave Jones
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