[Lguest] [PATCH] x86: initialize initial_page_table before paravirt jumps
Rusty Russell
rusty at rustcorp.com.au
Tue Jan 4 17:50:54 EST 2011
On Wed, 22 Dec 2010 12:59:00 pm Rusty Russell wrote:
> 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
> (da32dac10126 "lguest: populate initial_page_table"), now we fix it
> properly by doing that initialization before the paravirt jump.
Ping? Ingo? I don't see this in -tip...
Thanks,
Rusty.
Subject: x86: initialize initial_page_table before paravirt jumps
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
(da32dac10126 "lguest: populate initial_page_table"), now we fix it
properly by doing that initialization before the paravirt jump.
Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
Acked-by: Jeremy Fitzhardinge <jeremy at goop.org>
---
arch/x86/kernel/head_32.S | 77 ++++++++++++++++----------------
arch/x86/lguest/i386_head.S | 105 --------------------------------------------
2 files changed, 39 insertions(+), 143 deletions(-)
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -139,39 +139,6 @@ 1:
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
@@ -181,7 +148,6 @@ num_subarch_entries = (. - subarch_entri
*
* Note that the stack is not yet set up!
*/
-default_entry:
#ifdef CONFIG_X86_PAE
/*
@@ -261,7 +227,42 @@ 11:
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
@@ -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
@@ -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
diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S
--- a/arch/x86/lguest/i386_head.S
+++ b/arch/x86/lguest/i386_head.S
@@ -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
@@ -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
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