[PATCH 2/5] KVM: x86: MMU: Simplify force_pt_level calculation code in FNAME(page_fault)()

Takuya Yoshikawa
2015-10-16T07:52:20Z

As a bonus, an extra memory slot search can be eliminated when
is_self_change_mapping is true.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
---
arch/x86/kvm/paging_tmpl.h | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 07f1a4e..8ebc3a5 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -743,15 +743,14 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
&walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);

- if (walker.level >= PT_DIRECTORY_LEVEL)
- force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn)
- || is_self_change_mapping;
- else
+ if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
+ force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn);
+ if (!force_pt_level) {
+ level = min(walker.level, mapping_level(vcpu, walker.gfn));
+ walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
+ }
+ } else
force_pt_level = true;
- if (!force_pt_level) {
- level = min(walker.level, mapping_level(vcpu, walker.gfn));
- walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
- }

mmu_seq = vcpu->kvm->mmu_notifier_seq;
smp_rmb();
--
2.1.0