linux-kernel - Re: [tip:x86/asm] x86: Introduce GDT_ENTRY

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Message-ID: <4A768339.9060904@zytor.com>
Date:	Sun, 02 Aug 2009 23:27:05 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	akinobu.mita@...il.com, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86: Introduce GDT_ENTRY_INIT()

Ingo Molnar wrote:
> * tip-bot for Akinobu Mita <akinobu.mita@...il.com> wrote:
> 
>> Commit-ID:  d520da1173abd1f918b7e690220e14ba0fc56cfc
>> Gitweb:     http://git.kernel.org/tip/d520da1173abd1f918b7e690220e14ba0fc56cfc
>> Author:     Akinobu Mita <akinobu.mita@...il.com>
>> AuthorDate: Sun, 19 Jul 2009 00:12:20 +0900
>> Committer:  Ingo Molnar <mingo@...e.hu>
>> CommitDate: Sun, 19 Jul 2009 18:27:53 +0200
>>
>> x86: Introduce GDT_ENTRY_INIT()
>>
>> GDT_ENTRY_INIT is static initializer of desc_struct.
>>
>> We already have similar macro GDT_ENTRY() but it's static
>> initializer for u64 and it cannot be used for desc_struct.
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
>> LKML-Reference: <20090718151219.GD11294@...alhost.localdomain>
>> Signed-off-by: Ingo Molnar <mingo@...e.hu>
>>

OK, I spotted the following error, which certainly would explain a crash 
on an APM machine:

  	/* data */
-	[GDT_ENTRY_APMBIOS_BASE+2]	= { { { 0x0000ffff, 0x00409200 } } },
+	[GDT_ENTRY_APMBIOS_BASE+2]	= GDT_ENTRY_INIT(0x409a, 0, 0xffff),

Also, we shouldn't be initializing the A bits to clear unless we 
actually plan to check the A (and D) bits... that's just a waste of CPU 
cycles.

	-hpa


	-hpa
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