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KVM: switch to get_user_pages_fast

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Convert gfn_to_pfn to use get_user_pages_fast, which can do lockless
pagetable lookups on x86. Kernel compilation on 4-way guest is 3.7%
faster on VMX.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Marcelo Tosatti
2008-09-16 20:54:47 -03:00
committed by Avi Kivity
parent 777b3f49d2
commit 4c2155ce81
6 changed files with 15 additions and 38 deletions
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8
arch/x86/kvm/paging_tmpl.h
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@@ -102,14 +102,10 @@ static bool FNAME(cmpxchg_gpte)(struct kvm *kvm,
pt_element_t *table;
struct page *page;
down_read(&current->mm->mmap_sem);
page = gfn_to_page(kvm, table_gfn);
up_read(&current->mm->mmap_sem);
table = kmap_atomic(page, KM_USER0);
ret = CMPXCHG(&table[index], orig_pte, new_pte);
kunmap_atomic(table, KM_USER0);
kvm_release_page_dirty(page);
@@ -418,7 +414,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
return 0;
}
down_read(&current->mm->mmap_sem);
if (walker.level == PT_DIRECTORY_LEVEL) {
gfn_t large_gfn;
large_gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE-1);
@@ -428,9 +423,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
}
}
mmu_seq = vcpu->kvm->mmu_notifier_seq;
/* implicit mb(), we'll read before PT lock is unlocked */
smp_rmb();
pfn = gfn_to_pfn(vcpu->kvm, walker.gfn);
up_read(&current->mm->mmap_sem);
/* mmio */
if (is_error_pfn(pfn)) {