Attachment 146725 Details for Bug 224671 – Patch to fix the slow boot

[patch] Patch to fix the slow boot

fs-gs-clear (text/plain), 1.62 KB, created by Zachary Amsden on 2007-01-26 22:37:59 UTC

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Creator: Zachary Amsden

Created: 2007-01-26 22:37:59 UTC

Size: 1.62 KB

patch

obsolete

>Initialize FS and GS to __KERNEL_DS as well.  The actual value of them is not
>important, but it is important to reload them in protected mode.  At this time,
>they still retain the real mode values from initial boot.  VT disallows
>execution of code under such conditions, which means hardware virtualization
>can not be used to boot the kernel on Intel platforms, making the boot time
>painfully slow.
>
>This requires moving the GS load before the load of GS_BASE, so just move
>all the segments loads there to keep them together in the code.
>
>Signed-off-by: Zachary Amsden <zach@vmware.com>
>
>Index: linux-2.6.19/arch/x86_64/kernel/head.S
>===================================================================
>--- linux-2.6.19.orig/arch/x86_64/kernel/head.S	2006-11-29 13:57:37.000000000 -0800
>+++ linux-2.6.19/arch/x86_64/kernel/head.S	2007-01-11 16:57:24.000000000 -0800
>@@ -163,6 +163,20 @@ startup_64:
> 	 */
> 	lgdt	cpu_gdt_descr
> 
>+	/* set up data segments. actually 0 would do too */
>+	movl $__KERNEL_DS,%eax
>+	movl %eax,%ds	
>+	movl %eax,%ss
>+	movl %eax,%es
>+
>+	/*
>+	 * We don't really need to load %fs or %gs, but load them anyway
>+	 * to kill any stale realmode selectors.  This allows execution
>+	 * under VT hardware.
>+	 */
>+	movl %eax,%fs
>+	movl %eax,%gs
>+			
> 	/* 
> 	 * Setup up a dummy PDA. this is just for some early bootup code
> 	 * that does in_interrupt() 
>@@ -173,12 +187,6 @@ startup_64:
> 	shrq	$32,%rdx
> 	wrmsr	
> 
>-	/* set up data segments. actually 0 would do too */
>-	movl $__KERNEL_DS,%eax
>-	movl %eax,%ds	
>-	movl %eax,%ss
>-	movl %eax,%es
>-			
> 	/* esi is pointer to real mode structure with interesting info.
> 	   pass it to C */
> 	movl	%esi, %edi

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Attachments on bug 224671: 146725