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Subject[patch 08/21] Xen-paravirt: Allow paravirt backend to choose kernel PMD sharing
Xen does not allow guests to have the kernel pmd shared between page
tables, so parameterize pgtable.c to allow both modes of operation.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
--
arch/i386/kernel/paravirt.c | 1
arch/i386/mm/fault.c | 6 +--
arch/i386/mm/pageattr.c | 2 -
arch/i386/mm/pgtable.c | 61 +++++++++++++++++++------------
include/asm-i386/page.h | 7 ++-
include/asm-i386/paravirt.h | 1
include/asm-i386/pgtable-2level-defs.h | 2 +
include/asm-i386/pgtable-2level.h | 2 -
include/asm-i386/pgtable-3level-defs.h | 6 +++
include/asm-i386/pgtable-3level.h | 16 ++------
include/asm-i386/pgtable.h | 7 +++
11 files changed, 68 insertions(+), 43 deletions(-)
===================================================================
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -572,6 +572,7 @@ struct paravirt_ops paravirt_ops = {
.name = "bare hardware",
.paravirt_enabled = 0,
.kernel_rpl = 0,
+ .shared_kernel_pmd = 1, /* Only used when CONFIG_X86_PAE is set */

.patch = native_patch,
.banner = default_banner,
===================================================================
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -616,8 +616,7 @@ do_sigbus:
force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
}

-#ifndef CONFIG_X86_PAE
-void vmalloc_sync_all(void)
+void _vmalloc_sync_all(void)
{
/*
* Note that races in the updates of insync and start aren't
@@ -628,6 +627,8 @@ void vmalloc_sync_all(void)
static DECLARE_BITMAP(insync, PTRS_PER_PGD);
static unsigned long start = TASK_SIZE;
unsigned long address;
+
+ BUG_ON(SHARED_KERNEL_PMD);

BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK);
for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) {
@@ -651,4 +652,3 @@ void vmalloc_sync_all(void)
start = address + PGDIR_SIZE;
}
}
-#endif
===================================================================
--- a/arch/i386/mm/pageattr.c
+++ b/arch/i386/mm/pageattr.c
@@ -91,7 +91,7 @@ static void set_pmd_pte(pte_t *kpte, uns
unsigned long flags;

set_pte_atomic(kpte, pte); /* change init_mm */
- if (PTRS_PER_PMD > 1)
+ if (SHARED_KERNEL_PMD)
return;

spin_lock_irqsave(&pgd_lock, flags);
===================================================================
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -241,31 +241,42 @@ static void pgd_ctor(pgd_t *pgd)
unsigned long flags;

if (PTRS_PER_PMD == 1) {
+ /* !PAE, no pagetable sharing */
memset(pgd, 0, USER_PTRS_PER_PGD*sizeof(pgd_t));
+
+ clone_pgd_range(pgd + USER_PTRS_PER_PGD,
+ swapper_pg_dir + USER_PTRS_PER_PGD,
+ KERNEL_PGD_PTRS);
+
spin_lock_irqsave(&pgd_lock, flags);
- }
-
- clone_pgd_range(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);
+
+ /* 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);
+ } else {
+ /* PAE, PMD may be shared */
+ if (SHARED_KERNEL_PMD) {
+ clone_pgd_range((pgd_t *)pgd + USER_PTRS_PER_PGD,
+ swapper_pg_dir + USER_PTRS_PER_PGD,
+ KERNEL_PGD_PTRS);
+ } else {
+ spin_lock_irqsave(&pgd_lock, flags);
+ pgd_list_add(pgd);
+ spin_unlock_irqrestore(&pgd_lock, flags);
+ }
+ }
}

static void pgd_dtor(pgd_t *pgd)
{
unsigned long flags; /* can be called from interrupt context */

- if (PTRS_PER_PMD == 1)
+ if (SHARED_KERNEL_PMD)
return;

paravirt_release_pd(__pa(pgd) >> PAGE_SHIFT);
@@ -279,19 +290,25 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
int i;
pgd_t *pgd = kmem_cache_alloc(pgd_cache, GFP_KERNEL);

- if (pgd)
+ if (likely(pgd))
pgd_ctor(pgd);

- if (PTRS_PER_PMD == 1 || !pgd)
+ if (PTRS_PER_PMD == 1 || unlikely(!pgd))
return pgd;

- for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
+ for (i = 0; i < (SHARED_KERNEL_PMD ? USER_PTRS_PER_PGD : PTRS_PER_PGD); ++i) {
pmd_t *pmd = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
- if (!pmd)
+ if (unlikely(!pmd))
goto out_oom;
+
+ if (i >= USER_PTRS_PER_PGD)
+ memcpy(pmd, (void *)pgd_page_vaddr(swapper_pg_dir[i]),
+ sizeof(pmd_t) * PTRS_PER_PMD);
+
paravirt_alloc_pd(__pa(pmd) >> PAGE_SHIFT);
set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
}
+
return pgd;

out_oom:
@@ -312,7 +329,7 @@ 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 < (SHARED_KERNEL_PMD ? USER_PTRS_PER_PGD : PTRS_PER_PGD); ++i) {
pgd_t pgdent = pgd[i];
void* pmd = (void *)__va(pgd_val(pgdent)-1);
paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT);
===================================================================
--- a/include/asm-i386/page.h
+++ b/include/asm-i386/page.h
@@ -50,21 +50,23 @@ typedef struct { unsigned long long pgpr
#ifndef CONFIG_PARAVIRT
#define pmd_val(x) ((x).pmd)
#define pte_val(x) ((x).pte_low | ((unsigned long long)(x).pte_high << 32))
+#define __pte(x) ((pte_t) { .pte_low = (x), .pte_high = ((x) >> 32) } )
#define __pmd(x) ((pmd_t) { (x) } )
#endif /* CONFIG_PARAVIRT */
#define HPAGE_SHIFT 21
#include <asm-generic/pgtable-nopud.h>
-#else
+#else /* !CONFIG_X86_PAE */
typedef struct { unsigned long pte_low; } pte_t;
typedef struct { unsigned long pgd; } pgd_t;
typedef struct { unsigned long pgprot; } pgprot_t;
#define boot_pte_t pte_t /* or would you rather have a typedef */
#ifndef CONFIG_PARAVIRT
+#define __pte(x) ((pte_t) { (x) })
#define pte_val(x) ((x).pte_low)
#endif
#define HPAGE_SHIFT 22
#include <asm-generic/pgtable-nopmd.h>
-#endif
+#endif /* CONFIG_X86_PAE */
#define PTE_MASK PAGE_MASK

#ifdef CONFIG_HUGETLB_PAGE
@@ -79,7 +81,6 @@ typedef struct { unsigned long pgprot; }

#ifndef CONFIG_PARAVIRT
#define pgd_val(x) ((x).pgd)
-#define __pte(x) ((pte_t) { (x) } )
#define __pgd(x) ((pgd_t) { (x) } )
#endif

===================================================================
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -34,6 +34,7 @@ struct paravirt_ops
struct paravirt_ops
{
unsigned int kernel_rpl;
+ int shared_kernel_pmd;
int paravirt_enabled;
const char *name;

===================================================================
--- a/include/asm-i386/pgtable-2level-defs.h
+++ b/include/asm-i386/pgtable-2level-defs.h
@@ -1,5 +1,7 @@
#ifndef _I386_PGTABLE_2LEVEL_DEFS_H
#define _I386_PGTABLE_2LEVEL_DEFS_H
+
+#define SHARED_KERNEL_PMD 0

/*
* traditional i386 two-level paging structure:
===================================================================
--- a/include/asm-i386/pgtable-2level.h
+++ b/include/asm-i386/pgtable-2level.h
@@ -66,6 +66,4 @@ static inline int pte_exec_kernel(pte_t
#define __pte_to_swp_entry(pte) ((swp_entry_t) { (pte).pte_low })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })

-void vmalloc_sync_all(void);
-
#endif /* _I386_PGTABLE_2LEVEL_H */
===================================================================
--- a/include/asm-i386/pgtable-3level-defs.h
+++ b/include/asm-i386/pgtable-3level-defs.h
@@ -1,5 +1,11 @@
#ifndef _I386_PGTABLE_3LEVEL_DEFS_H
#define _I386_PGTABLE_3LEVEL_DEFS_H
+
+#ifdef CONFIG_PARAVIRT
+#define SHARED_KERNEL_PMD (paravirt_ops.shared_kernel_pmd)
+#else
+#define SHARED_KERNEL_PMD 1
+#endif

/*
* PGDIR_SHIFT determines what a top-level page table entry can map
===================================================================
--- a/include/asm-i386/pgtable-3level.h
+++ b/include/asm-i386/pgtable-3level.h
@@ -153,20 +153,14 @@ extern unsigned long long __supported_pt

static inline pte_t pfn_pte(unsigned long page_nr, pgprot_t pgprot)
{
- pte_t pte;
-
- pte.pte_high = (page_nr >> (32 - PAGE_SHIFT)) | \
- (pgprot_val(pgprot) >> 32);
- pte.pte_high &= (__supported_pte_mask >> 32);
- pte.pte_low = ((page_nr << PAGE_SHIFT) | pgprot_val(pgprot)) & \
- __supported_pte_mask;
- return pte;
+ return __pte((((unsigned long long)page_nr << PAGE_SHIFT) |
+ pgprot_val(pgprot)) & __supported_pte_mask);
}

static inline pmd_t pfn_pmd(unsigned long page_nr, pgprot_t pgprot)
{
- return __pmd((((unsigned long long)page_nr << PAGE_SHIFT) | \
- pgprot_val(pgprot)) & __supported_pte_mask);
+ return __pmd((((unsigned long long)page_nr << PAGE_SHIFT) |
+ pgprot_val(pgprot)) & __supported_pte_mask);
}

/*
@@ -186,6 +180,4 @@ static inline pmd_t pfn_pmd(unsigned lon

#define __pmd_free_tlb(tlb, x) do { } while (0)

-#define vmalloc_sync_all() ((void)0)
-
#endif /* _I386_PGTABLE_3LEVEL_H */
===================================================================
--- a/include/asm-i386/pgtable.h
+++ b/include/asm-i386/pgtable.h
@@ -239,6 +239,13 @@ static inline pte_t pte_mkwrite(pte_t pt
static inline pte_t pte_mkwrite(pte_t pte) { (pte).pte_low |= _PAGE_RW; return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { (pte).pte_low |= _PAGE_PSE; return pte; }

+extern void _vmalloc_sync_all(void);
+static inline void vmalloc_sync_all(void)
+{
+ if (!SHARED_KERNEL_PMD)
+ _vmalloc_sync_all();
+}
+
#ifdef CONFIG_X86_PAE
# include <asm/pgtable-3level.h>
#else
--

-
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