KVM: switch to get_user_pages_fast

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>

1 files changed, 0 insertions, 6 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 61eddbeabeb4..108f07267e87 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -946,10 +946,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
                 /* ...but clean it before doing the actual write */
                 vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
 
-                down_read(&current->mm->mmap_sem);
                 vcpu->arch.time_page =
                                 gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT);
-                up_read(&current->mm->mmap_sem);
 
                 if (is_error_page(vcpu->arch.time_page)) {
                         kvm_release_page_clean(vcpu->arch.time_page);
@@ -2322,9 +2320,7 @@ static int emulator_cmpxchg_emulated(unsigned long addr,
 
                 val = *(u64 *)new;
 
-                down_read(&current->mm->mmap_sem);
                 page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
-                up_read(&current->mm->mmap_sem);
 
                 kaddr = kmap_atomic(page, KM_USER0);
                 set_64bit((u64 *)(kaddr + offset_in_page(gpa)), val);
@@ -3089,9 +3085,7 @@ static void vapic_enter(struct kvm_vcpu *vcpu)
         if (!apic || !apic->vapic_addr)
                 return;
 
-        down_read(&current->mm->mmap_sem);
         page = gfn_to_page(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
-        up_read(&current->mm->mmap_sem);
 
         vcpu->arch.apic->vapic_page = page;
 }