[patch] pae-2.4.3-A4

Ingo Molnar
2001-03-25T14:53:37Z

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On Mon, 19 Mar 2001, Linus Torvalds wrote:

> The complete changelog is appended, but the biggest recent change is
> the mmap_sem change, which I updated with new locking rules for
> pte/pmd_alloc to avoid the race on the actual page table build.
>
> This has only been tested on i386 without PAE, and is known to break
> other architectures. Ingo, mind checking what PAE needs? [...]

one nontrivial issue was that on PAE the pgd has to be installed with
'present' pgd entries, due to a CPU erratum. This means that the
pgd_present() code in mm/memory.c, while correct theoretically, doesnt
work with PAE. An equivalent solution is to use !pgd_none(), which also
works with the PAE workaround.

PAE mode could re-define pgd_present() to filter out the workaround - do
you prefer this to the !pgd_none() solution?

the rest was pretty straightforward.

in any case, with the attached pae-2.4.3-A4 patch (against 2.4.3-pre7,
applies to 2.4.2-ac24 cleanly as well) applied, 2.4.3-pre7 boots & works
just fine on PAE 64GB-HIGHMEM and non-PAE kernels.

- the patch also does another cleanup: removes various bad_pagetable code
snippets all around the x86 tree, it's not needed anymore. This saves 8
KB RAM on x86 systems.

- removed the last remaining *_kernel() macro.

- fixed a minor clear_page() bug in pgalloc.h, gfp() could fail in the
future.

Ingo

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--- linux/mm/memory.c.orig Sun Mar 25 18:55:05 2001
+++ linux/mm/memory.c Sun Mar 25 18:55:07 2001
@@ -1295,7 +1295,7 @@
* Because we dropped the lock, we should re-check the
* entry, as somebody else could have populated it..
*/
- if (pgd_present(*pgd)) {
+ if (!pgd_none(*pgd)) {
pmd_free(new);
goto out;
}
@@ -1313,7 +1313,7 @@
*/
pte_t *pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
{
- if (!pmd_present(*pmd)) {
+ if (pmd_none(*pmd)) {
pte_t *new;

/* "fast" allocation can happen without dropping the lock.. */
@@ -1329,7 +1329,7 @@
* Because we dropped the lock, we should re-check the
* entry, as somebody else could have populated it..
*/
- if (pmd_present(*pmd)) {
+ if (!pmd_none(*pmd)) {
pte_free(new);
goto out;
}
--- linux/include/asm-i386/pgalloc-3level.h.orig Sun Mar 25 18:55:05 2001
+++ linux/include/asm-i386/pgalloc-3level.h Sun Mar 25 19:23:02 2001
@@ -21,12 +21,12 @@
{
unsigned long *ret;

- if ((ret = pmd_quicklist) != NULL) {
+ ret = pmd_quicklist;
+ if (ret != NULL) {
pmd_quicklist = (unsigned long *)(*ret);
ret[0] = 0;
pgtable_cache_size--;
- } else
- ret = (unsigned long *)get_pmd_slow();
+ }
return (pmd_t *)ret;
}

@@ -41,5 +41,10 @@
{
free_page((unsigned long)pmd);
}
+
+#define pmd_free(pmd) pmd_free_fast(pmd)
+
+#define pgd_populate(pgd, pmd) \
+ do { set_pgd(pgd, __pgd(1 + __pa(pmd))); __flush_tlb(); } while(0)

#endif /* _I386_PGALLOC_3LEVEL_H */
--- linux/include/asm-i386/pgalloc.h.orig Sun Mar 25 18:56:25 2001
+++ linux/include/asm-i386/pgalloc.h Sun Mar 25 19:35:59 2001
@@ -11,7 +11,8 @@
#define pte_quicklist (current_cpu_data.pte_quick)
#define pgtable_cache_size (current_cpu_data.pgtable_cache_sz)

-#define pmd_populate(pmd, pte) set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))
+#define pmd_populate(pmd, pte) \
+ set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))

#if CONFIG_X86_PAE
# include <asm/pgalloc-3level.h>
@@ -72,7 +73,8 @@
pte_t *pte;

pte = (pte_t *) __get_free_page(GFP_KERNEL);
- clear_page(pte);
+ if (pte)
+ clear_page(pte);
return pte;
}

@@ -100,7 +102,6 @@
free_page((unsigned long)pte);
}

-#define pte_free_kernel(pte) pte_free_slow(pte)
#define pte_free(pte) pte_free_slow(pte)
#define pgd_free(pgd) free_pgd_slow(pgd)
#define pgd_alloc() get_pgd_fast()
--- linux/include/asm-i386/pgtable.h.orig Sun Mar 25 19:03:58 2001
+++ linux/include/asm-i386/pgtable.h Sun Mar 25 19:04:06 2001
@@ -243,12 +243,6 @@
/* page table for 0-4MB for everybody */
extern unsigned long pg0[1024];

-/*
- * Handling allocation failures during page table setup.
- */
-extern void __handle_bad_pmd(pmd_t * pmd);
-extern void __handle_bad_pmd_kernel(pmd_t * pmd);
-
#define pte_present(x) ((x).pte_low & (_PAGE_PRESENT | _PAGE_PROTNONE))
#define pte_clear(xp) do { set_pte(xp, __pte(0)); } while (0)

--- linux/arch/i386/mm/init.c.orig Sun Mar 25 19:02:05 2001
+++ linux/arch/i386/mm/init.c Sun Mar 25 19:02:42 2001
@@ -40,77 +40,6 @@
static unsigned long totalram_pages;
static unsigned long totalhigh_pages;

-/*
- * BAD_PAGE is the page that is used for page faults when linux
- * is out-of-memory. Older versions of linux just did a
- * do_exit(), but using this instead means there is less risk
- * for a process dying in kernel mode, possibly leaving an inode
- * unused etc..
- *
- * BAD_PAGETABLE is the accompanying page-table: it is initialized
- * to point to BAD_PAGE entries.
- *
- * ZERO_PAGE is a special page that is used for zero-initialized
- * data and COW.
- */
-
-/*
- * These are allocated in head.S so that we get proper page alignment.
- * If you change the size of these then change head.S as well.
- */
-extern char empty_bad_page[PAGE_SIZE];
-#if CONFIG_X86_PAE
-extern pmd_t empty_bad_pmd_table[PTRS_PER_PMD];
-#endif
-extern pte_t empty_bad_pte_table[PTRS_PER_PTE];
-
-/*
- * We init them before every return and make them writable-shared.
- * This guarantees we get out of the kernel in some more or less sane
- * way.
- */
-#if CONFIG_X86_PAE
-static pmd_t * get_bad_pmd_table(void)
-{
- pmd_t v;
- int i;
-
- set_pmd(&v, __pmd(_PAGE_TABLE + __pa(empty_bad_pte_table)));
-
- for (i = 0; i < PAGE_SIZE/sizeof(pmd_t); i++)
- empty_bad_pmd_table[i] = v;
-
- return empty_bad_pmd_table;
-}
-#endif
-
-static pte_t * get_bad_pte_table(void)
-{
- pte_t v;
- int i;
-
- v = pte_mkdirty(mk_pte_phys(__pa(empty_bad_page), PAGE_SHARED));
-
- for (i = 0; i < PAGE_SIZE/sizeof(pte_t); i++)
- empty_bad_pte_table[i] = v;
-
- return empty_bad_pte_table;
-}
-
-
-
-void __handle_bad_pmd(pmd_t *pmd)
-{
- pmd_ERROR(*pmd);
- set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(get_bad_pte_table())));
-}
-
-void __handle_bad_pmd_kernel(pmd_t *pmd)
-{
- pmd_ERROR(*pmd);
- set_pmd(pmd, __pmd(_KERNPG_TABLE + __pa(get_bad_pte_table())));
-}
-
int do_check_pgt_cache(int low, int high)
{
int freed = 0;
--- linux/arch/i386/kernel/head.S.orig Sun Mar 25 19:04:23 2001
+++ linux/arch/i386/kernel/head.S Sun Mar 25 19:04:57 2001
@@ -415,23 +415,6 @@
ENTRY(empty_zero_page)

.org 0x5000
-ENTRY(empty_bad_page)
-
-.org 0x6000
-ENTRY(empty_bad_pte_table)
-
-#if CONFIG_X86_PAE
-
- .org 0x7000
- ENTRY(empty_bad_pmd_table)
-
- .org 0x8000
-
-#else
-
- .org 0x7000
-
-#endif

/*
* This starts the data section. Note that the above is all
--- linux/MAINTAINERS.orig Sun Mar 25 19:23:13 2001
+++ linux/MAINTAINERS Sun Mar 25 19:24:46 2001
@@ -1454,6 +1454,11 @@
L: linux-x25@vger.kernel.org
S: Maintained

+X86 3-LEVEL PAGING (PAE) SUPPORT
+P: Ingo Molnar
+M: mingo@redhat.com
+S: Maintained
+
Z85230 SYNCHRONOUS DRIVER
P: Alan Cox
M: alan@redhat.com