* Re: pgd_alloc and [cd]tors
2006-11-17 0:50 pgd_alloc and [cd]tors Jeremy Fitzhardinge
@ 2006-11-17 1:28 ` Chris Wright
2006-11-17 2:10 ` Zachary Amsden
1 sibling, 0 replies; 7+ messages in thread
From: Chris Wright @ 2006-11-17 1:28 UTC (permalink / raw)
To: Jeremy Fitzhardinge; +Cc: Chris Wright, Virtualization Mailing List
* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Is there any real use in having a ctor/dtor for the pgd cache? Given
> that all pgd allocation happens via pgd_alloc/pgd_free, why not just
> fold the [cd]tor in?
I don't see their value either.
> I'm asking because Xen wants pgd[3] to be unshared in the PAE case, and
> it looks to me like the easiest way to handle that is by making
> pgd_alloc/free pv-ops and doing the appropriate thing in the Xen code.
> Would need to sort out the vmalloc mapping replication as well, but I
> think that's pretty straightforward.
Here's an old patch from Zach that seems to address the issue at least
in part. It from back when we were doing subarch, but I think you can
see the attempt.
commit edb15f3f5e925d649b4dd28b0b430bea1a4c8fb4
Author: Zachary Amsden <zach@vmware.com>
Date: Wed Aug 24 14:43:14 2005 -0700
[PATCH] Add pagetable allocation notifiers
Hooks are provided for the mach-XXX subarchitecture at the time prior to a
page being used as a page table at all levels, for PAE and non-PAE kernels.
Note that in PAE mode, multiple PDP roots may exist on the same page with
other data, so the root must be shadowed instead. This is not a performance
issue, since PAE only uses 4 top level PDPEs.
The hooks are:
SetPagePTE(ppn) - indicates that a given physical page is going to be used
as a page table.
SetPagePDE(ppn) - indicates that a given physical page is going to be used
as a page directory.
ClearPageXXX(ppn) - indicates that the physical page is now done being
used as a certain type of page.
These hooks can be used in two ways; for shadow mode, they serve as
requests to pre-allocate and deallocate shadow page tables, and for
direct page table mode, they serve as write protect/unprotect requests.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>
diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index a65155e..853e5a9 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -59,6 +59,7 @@ static pmd_t * __init one_md_table_init(
#ifdef CONFIG_X86_PAE
pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+ SetPagePDE(virt_to_page(pmd_table));
set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
pud = pud_offset(pgd, 0);
if (pmd_table != pmd_offset(pud, 0))
@@ -79,6 +80,7 @@ static pte_t * __init one_page_table_ini
{
if (pmd_none(*pmd)) {
pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+ SetPagePTE(virt_to_page(page_table));
set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
if (page_table != pte_offset_kernel(pmd, 0))
BUG();
@@ -312,6 +314,7 @@ static void __init pagetable_init (void)
#ifdef CONFIG_X86_PAE
int i;
/* Init entries of the first-level page table to the zero page */
+ SetPagePDE(virt_to_page(empty_zero_page));
for (i = 0; i < PTRS_PER_PGD; i++)
set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
#endif
diff --git a/arch/i386/mm/pageattr.c b/arch/i386/mm/pageattr.c
index f600fc2..3c674b5 100644
--- a/arch/i386/mm/pageattr.c
+++ b/arch/i386/mm/pageattr.c
@@ -52,6 +52,7 @@ static struct page *split_large_page(uns
address = __pa(address);
addr = address & LARGE_PAGE_MASK;
pbase = (pte_t *)page_address(base);
+ SetPagePTE(virt_to_page(pbase));
for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
addr == address ? prot : PAGE_KERNEL));
@@ -146,6 +147,7 @@ __change_page_attr(struct page *page, pg
BUG_ON(!page_count(kpte_page));
if (cpu_has_pse && (page_count(kpte_page) == 1)) {
+ ClearPagePTE(virt_to_page(kpte));
list_add(&kpte_page->lru, &df_list);
revert_page(kpte_page, address);
}
diff --git a/arch/i386/mm/pgtable.c b/arch/i386/mm/pgtable.c
index dcdce2c..dd41ce2 100644
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -209,6 +209,7 @@ void pgd_ctor(void *pgd, kmem_cache_t *c
if (PTRS_PER_PMD == 1) {
memset(pgd, 0, USER_PTRS_PER_PGD*sizeof(pgd_t));
+ SetPagePDE(virt_to_page(pgd));
spin_lock_irqsave(&pgd_lock, flags);
}
@@ -227,6 +228,7 @@ void pgd_dtor(void *pgd, kmem_cache_t *c
{
unsigned long flags; /* can be called from interrupt context */
+ ClearPagePDE(virt_to_page(pgd));
spin_lock_irqsave(&pgd_lock, flags);
pgd_list_del(pgd);
spin_unlock_irqrestore(&pgd_lock, flags);
@@ -244,13 +246,16 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
pmd_t *pmd = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
if (!pmd)
goto out_oom;
+ SetPagePDE(virt_to_page(pmd));
set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
}
return pgd;
out_oom:
- for (i--; i >= 0; i--)
+ for (i--; i >= 0; i--) {
+ ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ }
kmem_cache_free(pgd_cache, pgd);
return NULL;
}
@@ -261,8 +266,10 @@ void pgd_free(pgd_t *pgd)
/* in the PAE case user pgd entries are overwritten before usage */
if (PTRS_PER_PMD > 1)
- for (i = 0; i < USER_PTRS_PER_PGD; ++i)
+ for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
+ ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ }
/* in the non-PAE case, free_pgtables() clears user pgd entries */
kmem_cache_free(pgd_cache, pgd);
}
diff --git a/include/asm-i386/mach-default/mach_pgalloc.h b/include/asm-i386/mach-default/mach_pgalloc.h
index 68e9bae..5ab6fed 100644
--- a/include/asm-i386/mach-default/mach_pgalloc.h
+++ b/include/asm-i386/mach-default/mach_pgalloc.h
@@ -1,7 +1,40 @@
+/*
+ * Copyright (C) 2005, VMware, Inc.
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * Send feedback to zach@vmware.com
+ *
+ */
#ifndef __ASM_MACH_PGALLOC_H
#define __ASM_MACH_PGALLOC_H
+/*
+ * These hooks allow the hypervisor to be notified about page type
+ * transition events.
+ */
+
+#define SetPagePTE(_page)
+#define ClearPagePTE(_page)
+#define SetPagePDE(_page)
+#define ClearPagePDE(_page)
+
#define SetPagesLDT(_va, _pages)
#define ClearPagesLDT(_va, _pages)
-#endif
+#endif /* _ASM_MACH_PGALLOC_H */
diff --git a/include/asm-i386/pgalloc.h b/include/asm-i386/pgalloc.h
index 0380c3d..d43978f 100644
--- a/include/asm-i386/pgalloc.h
+++ b/include/asm-i386/pgalloc.h
@@ -5,14 +5,22 @@
#include <asm/fixmap.h>
#include <linux/threads.h>
#include <linux/mm.h> /* for struct page */
+#include <mach_pgalloc.h>
-#define pmd_populate_kernel(mm, pmd, pte) \
- set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))
+#define pmd_populate_kernel(mm, pmd, pte) \
+do { \
+ SetPagePTE(virt_to_page(pte)); \
+ set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte))); \
+} while (0)
#define pmd_populate(mm, pmd, pte) \
+do { \
+ SetPagePTE(pte); \
set_pmd(pmd, __pmd(_PAGE_TABLE + \
((unsigned long long)page_to_pfn(pte) << \
- (unsigned long long) PAGE_SHIFT)))
+ (unsigned long long) PAGE_SHIFT))); \
+} while (0)
+
/*
* Allocate and free page tables.
*/
@@ -33,7 +41,11 @@ static inline void pte_free(struct page
}
-#define __pte_free_tlb(tlb,pte) tlb_remove_page((tlb),(pte))
+#define __pte_free_tlb(tlb,pte) \
+do { \
+ tlb_remove_page((tlb),(pte)); \
+ ClearPagePTE(pte); \
+} while (0)
#ifdef CONFIG_X86_PAE
/*
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