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xen: avoid hypercalls when updating unpinned pud/pmd

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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>
This commit is contained in:
Jeremy Fitzhardinge
2008-05-31 01:24:27 +01:00
committed by Ingo Molnar
parent 15ce60056b
commit e2426cf85f
3 changed files with 50 additions and 11 deletions
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14
arch/x86/xen/enlighten.c
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@@ -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,