lkml.org 
[lkml]   [2005]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/10] Cr4 is valid on some 486s
Pavel Machek wrote:

>Hi!
>
>
>
>>So some 486 processors do have CR4 register. Allow them to present it in
>>register dumps by using the old fault technique rather than testing processor
>>family.
>>
>>
>
>I thought Andi commented this as "way too risky", for little
>good. Nested exceptions are evil.
>
>

I didn't see Andi's comment to that effect. I may have originally
argued that when I made CR4 reads depend on CPU family. But I think it
is useful to know if PSE is enabled, especially on 486s that do support it.

Agree nested exceptions are evil. But where is this called from
execption context?

1) softlockup_tick appears to be perfectly safe call site to handle
exceptions
2) sysrq-p is also a fine site.

I tested this by assembling a hacked safe_read_cr1() macro, and dumped
the contents of my non-existant CR1 regsiter in show_regs to prove the
fault handling correct (although the code already _looks_ correct, I
thought someone might ask the question you just did. :)

Zach
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-11-11 20:41    [W:2.478 / U:2.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site