xen: avoid hypercalls when updating unpinned pud/pmd

When operating on an unpinned pagetable (ie, one under construction or
destruction), it isn't necessary to use a hypercall to update a
pud/pmd entry.  Jan Beulich observed that a similar optimisation
avoided many thousands of hypercalls while doing a kernel build.

One tricky part is that early in the kernel boot there's no page
structure, so we can't check to see if the page is pinned.  In that
case, we just always use the hypercall.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 3 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b94f63ac228b..ed9f04b3836d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -901,6 +901,14 @@ static __init void xen_pagetable_setup_done(pgd_t *base)
         pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(base)));
 }
 
+static __init void xen_post_allocator_init(void)
+{
+        pv_mmu_ops.set_pmd = xen_set_pmd;
+        pv_mmu_ops.set_pud = xen_set_pud;
+
+        xen_mark_init_mm_pinned();
+}
+
 /* This is called once we have the cpu_possible_map */
 void xen_setup_vcpu_info_placement(void)
 {
@@ -988,7 +996,7 @@ static const struct pv_init_ops xen_init_ops __initdata = {
         .banner = xen_banner,
         .memory_setup = xen_memory_setup,
         .arch_setup = xen_arch_setup,
-        .post_allocator_init = xen_mark_init_mm_pinned,
+        .post_allocator_init = xen_post_allocator_init,
 };
 
 static const struct pv_time_ops xen_time_ops __initdata = {
@@ -1100,7 +1108,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
 
         .set_pte = NULL,        /* see xen_pagetable_setup_* */
         .set_pte_at = xen_set_pte_at,
-        .set_pmd = xen_set_pmd,
+        .set_pmd = xen_set_pmd_hyper,
 
         .pte_val = xen_pte_val,
         .pte_flags = native_pte_val,
@@ -1111,7 +1119,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
 
         .set_pte_atomic = xen_set_pte_atomic,
         .set_pte_present = xen_set_pte_at,
-        .set_pud = xen_set_pud,
+        .set_pud = xen_set_pud_hyper,
         .pte_clear = xen_pte_clear,
         .pmd_clear = xen_pmd_clear,