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x86, mm: Initialize initial_page_table before paravirt jumps
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v2.6.36-rc8-54-gb40827f (x86-32, mm: Add an initial page table
for core bootstrapping) made x86 boot using initial_page_table
and broke lguest.

For 2.6.37 we simply cut & paste the initialization code into
lguest (da32dac "lguest: populate initial_page_table"), now
we fix it properly by doing that initialization before the
paravirt jump.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: lguest <lguest@ozlabs.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <201101041720.54535.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Rusty Russell authored and Ingo Molnar committed Jan 4, 2011
1 parent 387c31c commit d50d8fe
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Showing 2 changed files with 39 additions and 143 deletions.
77 changes: 39 additions & 38 deletions arch/x86/kernel/head_32.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -139,39 +139,6 @@ ENTRY(startup_32)
movl %eax, pa(olpc_ofw_pgd)
#endif

#ifdef CONFIG_PARAVIRT
/* This is can only trip for a broken bootloader... */
cmpw $0x207, pa(boot_params + BP_version)
jb default_entry

/* Paravirt-compatible boot parameters. Look to see what architecture
we're booting under. */
movl pa(boot_params + BP_hardware_subarch), %eax
cmpl $num_subarch_entries, %eax
jae bad_subarch

movl pa(subarch_entries)(,%eax,4), %eax
subl $__PAGE_OFFSET, %eax
jmp *%eax

bad_subarch:
WEAK(lguest_entry)
WEAK(xen_entry)
/* Unknown implementation; there's really
nothing we can do at this point. */
ud2a

__INITDATA

subarch_entries:
.long default_entry /* normal x86/PC */
.long lguest_entry /* lguest hypervisor */
.long xen_entry /* Xen hypervisor */
.long default_entry /* Moorestown MID */
num_subarch_entries = (. - subarch_entries) / 4
.previous
#endif /* CONFIG_PARAVIRT */

/*
* Initialize page tables. This creates a PDE and a set of page
* tables, which are located immediately beyond __brk_base. The variable
Expand All @@ -181,7 +148,6 @@ num_subarch_entries = (. - subarch_entries) / 4
*
* Note that the stack is not yet set up!
*/
default_entry:
#ifdef CONFIG_X86_PAE

/*
Expand Down Expand Up @@ -261,7 +227,42 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
movl %eax,pa(initial_page_table+0xffc)
#endif
jmp 3f

#ifdef CONFIG_PARAVIRT
/* This is can only trip for a broken bootloader... */
cmpw $0x207, pa(boot_params + BP_version)
jb default_entry

/* Paravirt-compatible boot parameters. Look to see what architecture
we're booting under. */
movl pa(boot_params + BP_hardware_subarch), %eax
cmpl $num_subarch_entries, %eax
jae bad_subarch

movl pa(subarch_entries)(,%eax,4), %eax
subl $__PAGE_OFFSET, %eax
jmp *%eax

bad_subarch:
WEAK(lguest_entry)
WEAK(xen_entry)
/* Unknown implementation; there's really
nothing we can do at this point. */
ud2a

__INITDATA

subarch_entries:
.long default_entry /* normal x86/PC */
.long lguest_entry /* lguest hypervisor */
.long xen_entry /* Xen hypervisor */
.long default_entry /* Moorestown MID */
num_subarch_entries = (. - subarch_entries) / 4
.previous
#else
jmp default_entry
#endif /* CONFIG_PARAVIRT */

/*
* Non-boot CPU entry point; entered from trampoline.S
* We can't lgdt here, because lgdt itself uses a data segment, but
Expand All @@ -282,7 +283,7 @@ ENTRY(startup_32_smp)
movl %eax,%fs
movl %eax,%gs
#endif /* CONFIG_SMP */
3:
default_entry:

/*
* New page tables may be in 4Mbyte page mode and may
Expand Down Expand Up @@ -622,13 +623,13 @@ ENTRY(initial_code)
__PAGE_ALIGNED_BSS
.align PAGE_SIZE_asm
#ifdef CONFIG_X86_PAE
ENTRY(initial_pg_pmd)
initial_pg_pmd:
.fill 1024*KPMDS,4,0
#else
ENTRY(initial_page_table)
.fill 1024,4,0
#endif
ENTRY(initial_pg_fixmap)
initial_pg_fixmap:
.fill 1024,4,0
ENTRY(empty_zero_page)
.fill 4096,1,0
Expand Down
105 changes: 0 additions & 105 deletions arch/x86/lguest/i386_head.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/processor-flags.h>
#include <asm/pgtable.h>

/*G:020
* Our story starts with the kernel booting into startup_32 in
Expand Down Expand Up @@ -38,113 +37,9 @@ ENTRY(lguest_entry)
/* Set up the initial stack so we can run C code. */
movl $(init_thread_union+THREAD_SIZE),%esp

call init_pagetables

/* Jumps are relative: we're running __PAGE_OFFSET too low. */
jmp lguest_init+__PAGE_OFFSET

/*
* Initialize page tables. This creates a PDE and a set of page
* tables, which are located immediately beyond __brk_base. The variable
* _brk_end is set up to point to the first "safe" location.
* Mappings are created both at virtual address 0 (identity mapping)
* and PAGE_OFFSET for up to _end.
*
* FIXME: This code is taken verbatim from arch/x86/kernel/head_32.S: they
* don't have a stack at this point, so we can't just use call and ret.
*/
init_pagetables:
#if PTRS_PER_PMD > 1
#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
#else
#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
#endif
#define pa(X) ((X) - __PAGE_OFFSET)

/* Enough space to fit pagetables for the low memory linear map */
MAPPING_BEYOND_END = \
PAGE_TABLE_SIZE(((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT) << PAGE_SHIFT
#ifdef CONFIG_X86_PAE

/*
* In PAE mode initial_page_table is statically defined to contain
* enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
* entries). The identity mapping is handled by pointing two PGD entries
* to the first kernel PMD.
*
* Note the upper half of each PMD or PTE are always zero at this stage.
*/

#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */

xorl %ebx,%ebx /* %ebx is kept at zero */

movl $pa(__brk_base), %edi
movl $pa(initial_pg_pmd), %edx
movl $PTE_IDENT_ATTR, %eax
10:
leal PDE_IDENT_ATTR(%edi),%ecx /* Create PMD entry */
movl %ecx,(%edx) /* Store PMD entry */
/* Upper half already zero */
addl $8,%edx
movl $512,%ecx
11:
stosl
xchgl %eax,%ebx
stosl
xchgl %eax,%ebx
addl $0x1000,%eax
loop 11b

/*
* End condition: we must map up to the end + MAPPING_BEYOND_END.
*/
movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
1:
addl $__PAGE_OFFSET, %edi
movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)

/* Do early initialization of the fixmap area */
movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
#else /* Not PAE */

page_pde_offset = (__PAGE_OFFSET >> 20);

movl $pa(__brk_base), %edi
movl $pa(initial_page_table), %edx
movl $PTE_IDENT_ATTR, %eax
10:
leal PDE_IDENT_ATTR(%edi),%ecx /* Create PDE entry */
movl %ecx,(%edx) /* Store identity PDE entry */
movl %ecx,page_pde_offset(%edx) /* Store kernel PDE entry */
addl $4,%edx
movl $1024, %ecx
11:
stosl
addl $0x1000,%eax
loop 11b
/*
* End condition: we must map up to the end + MAPPING_BEYOND_END.
*/
movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
addl $__PAGE_OFFSET, %edi
movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)

/* Do early initialization of the fixmap area */
movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
movl %eax,pa(initial_page_table+0xffc)
#endif
ret

/*G:055
* We create a macro which puts the assembler code between lgstart_ and lgend_
* markers. These templates are put in the .text section: they can't be
Expand Down

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