x86, mm: 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@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>

2 files changed, 39 insertions, 143 deletions

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index c0dbd9ac24f0..e3a8bb91e168 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -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
@@ -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
 
         /*
@@ -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
@@ -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
index e7d5382ef263..4f420c2f2d55 100644
--- 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