gorcunov at gmail
May 13, 2008, 10:14 AM
Post #6 of 6
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Re: [patch 1/2] x86: head_64.S cleanup - use straight move to CR4 register
[In reply to]
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[.H. Peter Anvin - Tue, May 13, 2008 at 10:11:34AM -0700]
> Cyrill Gorcunov wrote:
>> [.H. Peter Anvin - Tue, May 13, 2008 at 10:03:42AM -0700]
>>> Cyrill Gorcunov wrote:
>>>> There is no need for testing the values because we already know
>>>> what they should be. Just set them in straight way.
>>> He isn't testing them, he's setting individual bits.
>>>
>>> Either of these is pretty silly; the right way to do this is:
>>>
>>> movl $(X86_CR4_PAE|X86_CR4_PGE), %eax
>>> movq %rax, %cr4
>>>
>>> A movl in 64-bit mode zero extends.
>>>
>>> -hpa
>>>
>> Here is updated version
>> ---
>> [PATCH] x86: head_64.S cleanup - use straight move to CR4 register
>> Signed-off-by: Cyrill Gorcunov <gorcunov[at]gmail.com>
>> ---
>> Index: linux-2.6.git/arch/x86/kernel/head_64.S
>> ===================================================================
>> --- linux-2.6.git.orig/arch/x86/kernel/head_64.S 2008-05-13
>> 20:04:23.000000000 +0400
>> +++ linux-2.6.git/arch/x86/kernel/head_64.S 2008-05-13 21:08:20.000000000
>> +0400
>> @@ -155,9 +155,7 @@ ENTRY(secondary_startup_64)
>> */
>> /* Enable PAE mode and PGE */
>> - xorq %rax, %rax
>> - btsq $5, %rax
>> - btsq $7, %rax
>> + movl $(X86_CR4_PAE | X86_CR4_PGE), %rax
>> movq %rax, %cr4
>>
>
> Syntax error. %eax, not %rax.
>
> -hpa
>
Oh my, what I'm doing... sorry
Here we go
---
[PATCH] x86: head_64.S cleanup - use straight move to CR4 register
Signed-off-by: Cyrill Gorcunov <gorcunov[at]gmail.com>
---
Index: linux-2.6.git/arch/x86/kernel/head_64.S
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/head_64.S 2008-05-13 20:04:23.000000000 +0400
+++ linux-2.6.git/arch/x86/kernel/head_64.S 2008-05-13 21:12:39.000000000 +0400
@@ -155,9 +155,7 @@ ENTRY(secondary_startup_64)
*/
/* Enable PAE mode and PGE */
- xorq %rax, %rax
- btsq $5, %rax
- btsq $7, %rax
+ movl $(X86_CR4_PAE | X86_CR4_PGE), %eax
movq %rax, %cr4
/* Setup early boot stage 4 level pagetables. */
- Cyrill -
--
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