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>

3 files changed, 16 insertions, 5 deletions

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index e9b504537212..78c9a1b9e6b0 100644
--- 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>
@@ -366,6 +367,9 @@ struct pv_mmu_ops pv_mmu_ops = {
         .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
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);
 }
 
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 76ad1efaf09e..d62f14e20708 100644
--- 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"
@@ -1153,6 +1154,9 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
         .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,