Commit 08da5a2c authored Aug 10, 2007 by Zachary Amsden Committed by Linus Torvalds Aug 11, 2007

x86_64: Early segment setup for VT



VT is very picky about when it can enter execution.
Get all segments setup and get LDT and TR into valid state to allow
VT execution under VMware and KVM (untested).

This makes the boot decompression run under VT, which makes it several
orders of magnitude faster on 64-bit Intel hardware.

Before, I was seeing times up to a minute or more to decompress a 1.3MB kernel
on a very fast box.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ab144f5e

arch/x86_64/boot/compressed/head.S

+7 −0

Original line number	Diff line number	Diff line
		@@ -195,6 +195,11 @@ ENTRY(startup_64)
		movl %eax, %ds
		movl %eax, %es
		movl %eax, %ss
		movl %eax, %fs
		movl %eax, %gs
		lldt %ax
		movl $0x20, %eax
		ltr %ax

		/* Compute the decompressed kernel start address. It is where
		* we were loaded at aligned to a 2M boundary. %rbp contains the
		@@ -295,6 +300,8 @@ gdt:
		.quad 0x0000000000000000 /* NULL descriptor */
		.quad 0x00af9a000000ffff /* __KERNEL_CS */
		.quad 0x00cf92000000ffff /* __KERNEL_DS */
		.quad 0x0080890000000000 /* TS descriptor */
		.quad 0x0000000000000000 /* TS continued */
		gdt_end:
		.bss
		/* Stack for uncompression */