From: "H. Peter Anvin" <hpa@zytor.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: Ben Hutchings <ben@decadent.org.uk>,
x86@kernel.org, 584846@bugs.debian.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Bug#584846: Detects only 64MB and fails to boot on Intel Green City board if e820 hooked by GRUB2
Date: Thu, 24 Jun 2010 13:58:24 -0700 [thread overview]
Message-ID: <4C23C6F0.50206@zytor.com> (raw)
In-Reply-To: <20100624190107.GA15329@feather>
On 06/24/2010 12:01 PM, Josh Triplett wrote:
> On Thu, Jun 24, 2010 at 07:18:34AM -0700, H. Peter Anvin wrote:
>> On 06/24/2010 12:27 AM, Josh Triplett wrote:
>>> The following patch fixes GRUB; with this patch, I can reserve memory
>>> (such as with drivemap), boot 2.6.35-rc3 successfully, and it detects
>>> all of my RAM.
>>
>> Congratulations! You have just committed the single most common BIOS
>> implementation bug. (Sorry for the sarcasm, but this seems to be a bug
>> that almost everyone who tries to implement BIOS makes at one point or
>> another... even the original IBM BIOS had it in at least one place.)
>
> And a rather large number of sample interrupt code found on the web,
> including the e820 hook from the version of gPXE/Etherboot that I used
> as an example. :) Given that I just tested against Linux, which very
> carefully works around that particular BIOS bug, I didn't run into any
> issue.
>
> So, how high does GRUB's bug ("stc ; iret"/"clc ; iret") rank on the
> list of common BIOS implementation bugs?
>
Less common, since that one is apparently more obvious to people (you
only have to think one step ahead instead of two steps ahead.)
There is a reason Linux works around this and similar bugs... it truly
is extremely common (and does cause real problems in real code.)
-hpa
prev parent reply other threads:[~2010-06-24 20:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20100612060322.29053.94187.reportbug@feather>
2010-06-12 13:58 ` Bug#584846: Detects only 64MB and fails to boot on Intel Green City board if e820 hooked by GRUB2 Ben Hutchings
2010-06-12 18:28 ` H. Peter Anvin
2010-06-12 18:55 ` Josh Triplett
2010-06-12 20:41 ` H. Peter Anvin
2010-06-12 21:45 ` Josh Triplett
[not found] ` <20100612222634.GA1785@feather>
2010-06-12 23:01 ` H. Peter Anvin
2010-06-12 23:02 ` H. Peter Anvin
2010-06-13 0:07 ` Josh Triplett
2010-06-13 0:16 ` H. Peter Anvin
[not found] ` <20100622052236.GA9130@feather>
2010-06-22 6:07 ` H. Peter Anvin
2010-06-22 16:07 ` Josh Triplett
2010-06-24 7:27 ` Josh Triplett
2010-06-24 14:18 ` H. Peter Anvin
2010-06-24 19:01 ` Josh Triplett
2010-06-24 20:58 ` H. Peter Anvin [this message]
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