x86/paravirt: add a pgd_alloc/free hooks

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.

also fix:

> * Ingo Molnar <mingo@elte.hu> wrote:
>
>  include/asm/pgalloc.h: In function ‘paravirt_pgd_free':
>  include/asm/pgalloc.h:14: error: parameter name omitted
>  arch/x86/kernel/entry_64.S: In file included from
>  arch/x86/kernel/traps_64.c:51:include/asm/pgalloc.h: In function ‘paravirt_pgd_free':
>  include/asm/pgalloc.h:14: error: parameter name omitted

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 5 deletions

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 45b99ac39480..418c4432fb39 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -215,13 +215,15 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 
         /* 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 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 {
         pgd_mop_up_pmds(mm, pgd);
         pgd_dtor(pgd);
+        paravirt_pgd_free(mm, pgd);
         free_page((unsigned long)pgd);
 }