[Xen-devel] [PATCH 16 of 36] x86/paravirt: add a pgd_alloc/free hooks

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Add hooks which are called at pgd_alloc/free time.  The pgd_alloc hook
may return an error code, which if non-zero, causes the pgd allocation
to be failed.  The hooks may be used to allocate/free auxillary
per-pgd information.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/kernel/paravirt.c |    4 ++++
 arch/x86/mm/pgtable.c      |   13 ++++++++-----
 arch/x86/xen/enlighten.c   |    4 ++++
 include/asm-x86/paravirt.h |   19 ++++++++++++++++++-
 include/asm-x86/pgalloc.h  |    4 ++++
 5 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -30,6 +30,7 @@
 #include <asm/setup.h>
 #include <asm/arch_hooks.h>
 #include <asm/time.h>
+#include <asm/pgalloc.h>
 #include <asm/irq.h>
 #include <asm/delay.h>
 #include <asm/fixmap.h>
@@ -369,6 +370,9 @@
        .flush_tlb_single = native_flush_tlb_single,
        .flush_tlb_others = native_flush_tlb_others,
 
+       .pgd_alloc = __paravirt_pgd_alloc,
+       .pgd_free = paravirt_nop,
+
        .alloc_pte = paravirt_nop,
        .alloc_pmd = paravirt_nop,
        .alloc_pmd_clone = paravirt_nop,
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -215,13 +215,15 @@
 
        /* so that alloc_pmd can use it */
        mm->pgd = pgd;
-       if (pgd)
+       if (pgd) {
                pgd_ctor(pgd);
 
-       if (pgd && !pgd_prepopulate_pmd(mm, pgd)) {
-               pgd_dtor(pgd);
-               free_page((unsigned long)pgd);
-               pgd = NULL;
+               if (paravirt_pgd_alloc(mm) != 0 ||
+                   !pgd_prepopulate_pmd(mm, pgd)) {
+                       pgd_dtor(pgd);
+                       free_page((unsigned long)pgd);
+                       pgd = NULL;
+               }
        }
 
        return pgd;
@@ -231,6 +233,7 @@
 {
        pgd_mop_up_pmds(mm, pgd);
        pgd_dtor(pgd);
+       paravirt_pgd_free(mm, pgd);
        free_page((unsigned long)pgd);
 }
 
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -45,6 +45,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/reboot.h>
+#include <asm/pgalloc.h>
 
 #include "xen-ops.h"
 #include "mmu.h"
@@ -1151,6 +1152,9 @@
        .pte_update = paravirt_nop,
        .pte_update_defer = paravirt_nop,
 
+       .pgd_alloc = __paravirt_pgd_alloc,
+       .pgd_free = paravirt_nop,
+
        .alloc_pte = xen_alloc_pte_init,
        .release_pte = xen_release_pte_init,
        .alloc_pmd = xen_alloc_pte_init,
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -220,7 +220,14 @@
        void (*flush_tlb_others)(const cpumask_t *cpus, struct mm_struct *mm,
                                 unsigned long va);
 
-       /* Hooks for allocating/releasing pagetable pages */
+       /* Hooks for allocating and freeing a pagetable top-level */
+       int  (*pgd_alloc)(struct mm_struct *mm);
+       void (*pgd_free)(struct mm_struct *mm, pgd_t *pgd);
+
+       /*
+        * Hooks for allocating/releasing pagetable pages when they're
+        * attached to a pagetable
+        */
        void (*alloc_pte)(struct mm_struct *mm, u32 pfn);
        void (*alloc_pmd)(struct mm_struct *mm, u32 pfn);
        void (*alloc_pmd_clone)(u32 pfn, u32 clonepfn, u32 start, u32 count);
@@ -926,6 +933,16 @@
        PVOP_VCALL3(pv_mmu_ops.flush_tlb_others, &cpumask, mm, va);
 }
 
+static inline int paravirt_pgd_alloc(struct mm_struct *mm)
+{
+       return PVOP_CALL1(int, pv_mmu_ops.pgd_alloc, mm);
+}
+
+static inline void paravirt_pgd_free(struct mm_struct *mm, pgd_t *pgd)
+{
+       PVOP_VCALL2(pv_mmu_ops.pgd_free, mm, pgd);
+}
+
 static inline void paravirt_alloc_pte(struct mm_struct *mm, unsigned pfn)
 {
        PVOP_VCALL2(pv_mmu_ops.alloc_pte, mm, pfn);
diff --git a/include/asm-x86/pgalloc.h b/include/asm-x86/pgalloc.h
--- a/include/asm-x86/pgalloc.h
+++ b/include/asm-x86/pgalloc.h
@@ -5,9 +5,13 @@
 #include <linux/mm.h>          /* for struct page */
 #include <linux/pagemap.h>
 
+static inline int  __paravirt_pgd_alloc(struct mm_struct *mm) { return 0; }
+
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else
+#define paravirt_pgd_alloc(mm) __paravirt_pgd_alloc(mm)
+static inline void paravirt_pgd_free(struct mm_struct *mm, pgd_t *) {}
 static inline void paravirt_alloc_pte(struct mm_struct *mm, unsigned long pfn) 
{}
 static inline void paravirt_alloc_pmd(struct mm_struct *mm, unsigned long pfn) 
{}
 static inline void paravirt_alloc_pmd_clone(unsigned long pfn, unsigned long 
clonepfn,



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