Commit a6523748 authored by Eduardo Habkost's avatar Eduardo Habkost Committed by Ingo Molnar
Browse files

paravirt/x86, 64-bit: move __PAGE_OFFSET to leave a space for hypervisor 



Set __PAGE_OFFSET to the most negative possible address +
16*PGDIR_SIZE.  The gap is to allow a space for a hypervisor to fit.
The gap is more or less arbitrary, but it's what Xen needs.

When booting native, kernel/head_64.S has a set of compile-time
generated pagetables used at boot time.  This patch removes their
absolutely hard-coded layout, and makes it parameterised on
__PAGE_OFFSET (and __START_KERNEL_map).

Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 491eccb7

arch/x86/kernel/head_64.S

+12 −5
Original line number Diff line number Diff line
@@ -32,6 +32,13 @@ 
 *

 */



#define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))



L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)

L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)

L4_START_KERNEL = pgd_index(__START_KERNEL_map)

L3_START_KERNEL = pud_index(__START_KERNEL_map)



	.text

	.section .text.head

	.code64
@@ -77,8 +84,8 @@ startup_64: 
	/* Fixup the physical addresses in the page table

	 */

	addq	%rbp, init_level4_pgt + 0(%rip)

	addq	%rbp, init_level4_pgt + (258*8)(%rip)

	addq	%rbp, init_level4_pgt + (511*8)(%rip)

	addq	%rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip)

	addq	%rbp, init_level4_pgt + (L4_START_KERNEL*8)(%rip)



	addq	%rbp, level3_ident_pgt + 0(%rip)
@@ -338,9 +345,9 @@ ENTRY(name) 
	 */

NEXT_PAGE(init_level4_pgt)

	.quad	level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE

	.fill	257,8,0

	.org	init_level4_pgt + L4_PAGE_OFFSET*8, 0

	.quad	level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE

	.fill	252,8,0

	.org	init_level4_pgt + L4_START_KERNEL*8, 0

	/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */

	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
@@ -349,7 +356,7 @@ NEXT_PAGE(level3_ident_pgt) 
	.fill	511,8,0



NEXT_PAGE(level3_kernel_pgt)

	.fill	510,8,0

	.fill	L3_START_KERNEL,8,0

	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */

	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE

	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE

include/asm-x86/page_64.h

+7 −1
Original line number Diff line number Diff line
@@ -26,7 +26,13 @@ 
#define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)

#define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))



#define __PAGE_OFFSET           _AC(0xffff810000000000, UL)

/*

 * Set __PAGE_OFFSET to the most negative possible address +

 * PGDIR_SIZE*16 (pgd slot 272).  The gap is to allow a space for a

 * hypervisor to fit.  Choosing 16 slots here is arbitrary, but it's

 * what Xen requires.

 */

#define __PAGE_OFFSET           _AC(0xffff880000000000, UL)



#define __PHYSICAL_START	CONFIG_PHYSICAL_START

#define __KERNEL_ALIGN		0x200000

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