[PATCH] MM: page allocation hooks for VMI backend
The VMI backend uses explicit page type notification to track shadow page
tables. The allocation of page table roots is especially tricky. We need to
clone the root for non-PAE mode while it is protected under the pgd lock to
correctly copy the shadow.
We don't need to allocate pgds in PAE mode, (PDPs in Intel terminology) as
they only have 4 entries, and are cached entirely by the processor, which
makes shadowing them rather simple.
For base page table level allocation, pmd_populate provides the exact hook
point we need. Also, we need to allocate pages when splitting a large page,
and we must release pages before returning the page to any free pool.
Despite being required with these slightly odd semantics for VMI, Xen also
uses these hooks to determine the exact moment when page tables are created or
released.
AK: All nops for other architectures
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index e55fd05..7329ec9 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -550,6 +550,12 @@
.flush_tlb_kernel = native_flush_tlb_global,
.flush_tlb_single = native_flush_tlb_single,
+ .alloc_pt = (void *)native_nop,
+ .alloc_pd = (void *)native_nop,
+ .alloc_pd_clone = (void *)native_nop,
+ .release_pt = (void *)native_nop,
+ .release_pd = (void *)native_nop,
+
.set_pte = native_set_pte,
.set_pte_at = native_set_pte_at,
.set_pmd = native_set_pmd,
diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index c5c5ea7..ae43688 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -62,6 +62,7 @@
#ifdef CONFIG_X86_PAE
pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+ paravirt_alloc_pd(__pa(pmd_table) >> PAGE_SHIFT);
set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
pud = pud_offset(pgd, 0);
if (pmd_table != pmd_offset(pud, 0))
@@ -82,6 +83,7 @@
{
if (pmd_none(*pmd)) {
pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+ paravirt_alloc_pt(__pa(page_table) >> PAGE_SHIFT);
set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
if (page_table != pte_offset_kernel(pmd, 0))
BUG();
@@ -345,6 +347,8 @@
/* Init entries of the first-level page table to the zero page */
for (i = 0; i < PTRS_PER_PGD; i++)
set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
+#else
+ paravirt_alloc_pd(__pa(swapper_pg_dir) >> PAGE_SHIFT);
#endif
/* Enable PSE if available */
diff --git a/arch/i386/mm/pageattr.c b/arch/i386/mm/pageattr.c
index e223b1d..412ebbd 100644
--- a/arch/i386/mm/pageattr.c
+++ b/arch/i386/mm/pageattr.c
@@ -60,6 +60,7 @@
address = __pa(address);
addr = address & LARGE_PAGE_MASK;
pbase = (pte_t *)page_address(base);
+ paravirt_alloc_pt(page_to_pfn(base));
for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
addr == address ? prot : ref_prot));
@@ -172,6 +173,7 @@
if (!PageReserved(kpte_page)) {
if (cpu_has_pse && (page_private(kpte_page) == 0)) {
ClearPagePrivate(kpte_page);
+ paravirt_release_pt(page_to_pfn(kpte_page));
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 f349eaf..b5f538f 100644
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -248,9 +248,15 @@
clone_pgd_range((pgd_t *)pgd + USER_PTRS_PER_PGD,
swapper_pg_dir + USER_PTRS_PER_PGD,
KERNEL_PGD_PTRS);
+
if (PTRS_PER_PMD > 1)
return;
+ /* must happen under lock */
+ paravirt_alloc_pd_clone(__pa(pgd) >> PAGE_SHIFT,
+ __pa(swapper_pg_dir) >> PAGE_SHIFT,
+ USER_PTRS_PER_PGD, PTRS_PER_PGD - USER_PTRS_PER_PGD);
+
pgd_list_add(pgd);
spin_unlock_irqrestore(&pgd_lock, flags);
}
@@ -260,6 +266,7 @@
{
unsigned long flags; /* can be called from interrupt context */
+ paravirt_release_pd(__pa(pgd) >> PAGE_SHIFT);
spin_lock_irqsave(&pgd_lock, flags);
pgd_list_del(pgd);
spin_unlock_irqrestore(&pgd_lock, flags);
@@ -277,13 +284,18 @@
pmd_t *pmd = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
if (!pmd)
goto out_oom;
+ paravirt_alloc_pd(__pa(pmd) >> PAGE_SHIFT);
set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
}
return pgd;
out_oom:
- for (i--; i >= 0; i--)
- kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ for (i--; i >= 0; i--) {
+ pgd_t pgdent = pgd[i];
+ void* pmd = (void *)__va(pgd_val(pgdent)-1);
+ paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT);
+ kmem_cache_free(pmd_cache, pmd);
+ }
kmem_cache_free(pgd_cache, pgd);
return NULL;
}
@@ -294,8 +306,12 @@
/* 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)
- kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
+ pgd_t pgdent = pgd[i];
+ void* pmd = (void *)__va(pgd_val(pgdent)-1);
+ paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT);
+ kmem_cache_free(pmd_cache, pmd);
+ }
/* in the non-PAE case, free_pgtables() clears user pgd entries */
kmem_cache_free(pgd_cache, pgd);
}
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 9f06265..53da276 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -127,6 +127,12 @@
void (fastcall *flush_tlb_kernel)(void);
void (fastcall *flush_tlb_single)(u32 addr);
+ void (fastcall *alloc_pt)(u32 pfn);
+ void (fastcall *alloc_pd)(u32 pfn);
+ void (fastcall *alloc_pd_clone)(u32 pfn, u32 clonepfn, u32 start, u32 count);
+ void (fastcall *release_pt)(u32 pfn);
+ void (fastcall *release_pd)(u32 pfn);
+
void (fastcall *set_pte)(pte_t *ptep, pte_t pteval);
void (fastcall *set_pte_at)(struct mm_struct *mm, u32 addr, pte_t *ptep, pte_t pteval);
void (fastcall *set_pmd)(pmd_t *pmdp, pmd_t pmdval);
@@ -320,6 +326,14 @@
#define __flush_tlb_global() paravirt_ops.flush_tlb_kernel()
#define __flush_tlb_single(addr) paravirt_ops.flush_tlb_single(addr)
+#define paravirt_alloc_pt(pfn) paravirt_ops.alloc_pt(pfn)
+#define paravirt_release_pt(pfn) paravirt_ops.release_pt(pfn)
+
+#define paravirt_alloc_pd(pfn) paravirt_ops.alloc_pd(pfn)
+#define paravirt_alloc_pd_clone(pfn, clonepfn, start, count) \
+ paravirt_ops.alloc_pd_clone(pfn, clonepfn, start, count)
+#define paravirt_release_pd(pfn) paravirt_ops.release_pd(pfn)
+
static inline void set_pte(pte_t *ptep, pte_t pteval)
{
paravirt_ops.set_pte(ptep, pteval);
diff --git a/include/asm-i386/pgalloc.h b/include/asm-i386/pgalloc.h
index 4b1e613..c8dc2d0 100644
--- a/include/asm-i386/pgalloc.h
+++ b/include/asm-i386/pgalloc.h
@@ -5,13 +5,31 @@
#include <linux/threads.h>
#include <linux/mm.h> /* for struct page */
-#define pmd_populate_kernel(mm, pmd, pte) \
- set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#else
+#define paravirt_alloc_pt(pfn) do { } while (0)
+#define paravirt_alloc_pd(pfn) do { } while (0)
+#define paravirt_alloc_pd(pfn) do { } while (0)
+#define paravirt_alloc_pd_clone(pfn, clonepfn, start, count) do { } while (0)
+#define paravirt_release_pt(pfn) do { } while (0)
+#define paravirt_release_pd(pfn) do { } while (0)
+#endif
+
+#define pmd_populate_kernel(mm, pmd, pte) \
+do { \
+ paravirt_alloc_pt(__pa(pte) >> PAGE_SHIFT); \
+ set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte))); \
+} while (0)
#define pmd_populate(mm, pmd, pte) \
+do { \
+ paravirt_alloc_pt(page_to_pfn(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.
*/
@@ -32,7 +50,11 @@
}
-#define __pte_free_tlb(tlb,pte) tlb_remove_page((tlb),(pte))
+#define __pte_free_tlb(tlb,pte) \
+do { \
+ paravirt_release_pt(page_to_pfn(pte)); \
+ tlb_remove_page((tlb),(pte)); \
+} while (0)
#ifdef CONFIG_X86_PAE
/*