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Subject[PATCH 2/8] x86/head: Refactor 32-bit pgtable setup
Date
From: Matt Fleming <matt@codeblueprint.co.uk>

The new Xen PVH entry point requires page tables to be setup by the
kernel since it is entered with paging disabled.

Pull the common code out of head_32.S and into pgtable_32.S so that
setup_pgtable_32 can be invoked from both the new Xen entry point and
the existing startup_32 code.

Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
---
arch/x86/Makefile | 2 +
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/head_32.S | 168 +------------------------------------
arch/x86/kernel/pgtable_32.S | 196 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 201 insertions(+), 167 deletions(-)
create mode 100644 arch/x86/kernel/pgtable_32.S

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 2d44933..67cc771 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -204,6 +204,8 @@ head-y += arch/x86/kernel/head$(BITS).o
head-y += arch/x86/kernel/ebda.o
head-y += arch/x86/kernel/platform-quirks.o

+head-$(CONFIG_X86_32) += arch/x86/kernel/pgtable_32.o
+
libs-y += arch/x86/lib/

# See arch/x86/Kbuild for content of core part of the kernel
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4dd5d50..eae85a5 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -8,6 +8,8 @@ extra-y += ebda.o
extra-y += platform-quirks.o
extra-y += vmlinux.lds

+extra-$(CONFIG_X86_32) += pgtable_32.o
+
CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)

ifdef CONFIG_FUNCTION_TRACER
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 5f40126..0db066e 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -41,51 +41,6 @@
#define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id

/*
- * This is how much memory in addition to the memory covered up to
- * and including _end we need mapped initially.
- * We need:
- * (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
- * (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
- *
- * Modulo rounding, each megabyte assigned here requires a kilobyte of
- * memory, which is currently unreclaimed.
- *
- * This should be a multiple of a page.
- *
- * KERNEL_IMAGE_SIZE should be greater than pa(_end)
- * and small than max_low_pfn, otherwise will waste some page table entries
- */
-
-#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
-
-/*
- * Number of possible pages in the lowmem region.
- *
- * We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
- * gas warning about overflowing shift count when gas has been compiled
- * with only a host target support using a 32-bit type for internal
- * representation.
- */
-LOWMEM_PAGES = (((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT)
-
-/* Enough space to fit pagetables for the low memory linear map */
-MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
-
-/*
- * Worst-case size of the kernel mapping we need to make:
- * a relocatable kernel can live anywhere in lowmem, so we need to be able
- * to map all of lowmem.
- */
-KERNEL_PAGES = LOWMEM_PAGES
-
-INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
-RESERVE_BRK(pagetables, INIT_MAP_SIZE)
-
-/*
* 32-bit kernel entrypoint; only used by the boot CPU. On entry,
* %esi points to the real-mode code as a 32-bit pointer.
* CS and DS must be 4 GB flat segments, but we don't depend on
@@ -157,92 +112,7 @@ ENTRY(startup_32)
call load_ucode_bsp
#endif

-/*
- * 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.
- */
-#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
+ call setup_pgtable_32

#ifdef CONFIG_PARAVIRT
/* This is can only trip for a broken bootloader... */
@@ -660,47 +530,11 @@ ENTRY(setup_once_ref)
*/
__PAGE_ALIGNED_BSS
.align PAGE_SIZE
-#ifdef CONFIG_X86_PAE
-initial_pg_pmd:
- .fill 1024*KPMDS,4,0
-#else
-ENTRY(initial_page_table)
- .fill 1024,4,0
-#endif
-initial_pg_fixmap:
- .fill 1024,4,0
ENTRY(empty_zero_page)
.fill 4096,1,0
ENTRY(swapper_pg_dir)
.fill 1024,4,0

-/*
- * This starts the data section.
- */
-#ifdef CONFIG_X86_PAE
-__PAGE_ALIGNED_DATA
- /* Page-aligned for the benefit of paravirt? */
- .align PAGE_SIZE
-ENTRY(initial_page_table)
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0 /* low identity map */
-# if KPMDS == 3
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
-# elif KPMDS == 2
- .long 0,0
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
-# elif KPMDS == 1
- .long 0,0
- .long 0,0
- .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
-# else
-# error "Kernel PMDs should be 1, 2 or 3"
-# endif
- .align PAGE_SIZE /* needs to be page-sized too */
-#endif
-
.data
.balign 4
ENTRY(initial_stack)
diff --git a/arch/x86/kernel/pgtable_32.S b/arch/x86/kernel/pgtable_32.S
new file mode 100644
index 0000000..aded718
--- /dev/null
+++ b/arch/x86/kernel/pgtable_32.S
@@ -0,0 +1,196 @@
+#include <linux/threads.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page_types.h>
+#include <asm/pgtable_types.h>
+#include <asm/cache.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
+#include <asm/setup.h>
+#include <asm/processor-flags.h>
+#include <asm/msr-index.h>
+#include <asm/cpufeatures.h>
+#include <asm/percpu.h>
+#include <asm/nops.h>
+#include <asm/bootparam.h>
+
+/* Physical address */
+#define pa(X) ((X) - __PAGE_OFFSET)
+
+/*
+ * This is how much memory in addition to the memory covered up to
+ * and including _end we need mapped initially.
+ * We need:
+ * (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
+ * (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
+ *
+ * Modulo rounding, each megabyte assigned here requires a kilobyte of
+ * memory, which is currently unreclaimed.
+ *
+ * This should be a multiple of a page.
+ *
+ * KERNEL_IMAGE_SIZE should be greater than pa(_end)
+ * and small than max_low_pfn, otherwise will waste some page table entries
+ */
+
+#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
+
+/*
+ * Number of possible pages in the lowmem region.
+ *
+ * We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
+ * gas warning about overflowing shift count when gas has been compiled
+ * with only a host target support using a 32-bit type for internal
+ * representation.
+ */
+LOWMEM_PAGES = (((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT)
+
+/* Enough space to fit pagetables for the low memory linear map */
+MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
+
+/*
+ * Worst-case size of the kernel mapping we need to make:
+ * a relocatable kernel can live anywhere in lowmem, so we need to be able
+ * to map all of lowmem.
+ */
+KERNEL_PAGES = LOWMEM_PAGES
+
+INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
+RESERVE_BRK(pagetables, INIT_MAP_SIZE)
+
+/*
+ * 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.
+ */
+ .text
+ENTRY(setup_pgtable_32)
+#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
+ENDPROC(setup_pgtable_32)
+
+/*
+ * BSS section
+ */
+__PAGE_ALIGNED_BSS
+ .align PAGE_SIZE
+#ifdef CONFIG_X86_PAE
+initial_pg_pmd:
+ .fill 1024*KPMDS,4,0
+#else
+ENTRY(initial_page_table)
+ .fill 1024,4,0
+#endif
+initial_pg_fixmap:
+ .fill 1024,4,0
+
+/*
+ * This starts the data section.
+ */
+#ifdef CONFIG_X86_PAE
+__PAGE_ALIGNED_DATA
+ /* Page-aligned for the benefit of paravirt? */
+ .align PAGE_SIZE
+ENTRY(initial_page_table)
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0 /* low identity map */
+# if KPMDS == 3
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
+# elif KPMDS == 2
+ .long 0,0
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
+# elif KPMDS == 1
+ .long 0,0
+ .long 0,0
+ .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+# else
+# error "Kernel PMDs should be 1, 2 or 3"
+# endif
+ .align PAGE_SIZE /* needs to be page-sized too */
+#endif
--
1.8.3.1
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