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KVM: MMU: Add unlikely() annotations to walk_addr_generic()

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walk_addr_generic() is a hot path and is also hard for the cpu to predict -
some of the parameters (fetch_fault in particular) vary wildly from
invocation to invocation.

Add unlikely() annotations where appropriate; all walk failures are
considered unlikely, as are cases where we have to mark the accessed or
dirty bit, as they are slow paths both in kvm and on real processors.

Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity 2011-04-24 12:25:50 +03:00
parent 62aaa2f05a
commit 781e0743af
1 changed files with 15 additions and 13 deletions
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28
arch/x86/kvm/paging_tmpl.h
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@ -172,49 +172,51 @@ walk:
real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
PFERR_USER_MASK|PFERR_WRITE_MASK);
if (real_gfn == UNMAPPED_GVA) {
if (unlikely(real_gfn == UNMAPPED_GVA)) {
present = false;
break;
}
real_gfn = gpa_to_gfn(real_gfn);
host_addr = gfn_to_hva(vcpu->kvm, real_gfn);
if (kvm_is_error_hva(host_addr)) {
if (unlikely(kvm_is_error_hva(host_addr))) {
present = false;
break;
}
ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
if (get_user(pte, ptep_user)) {
if (unlikely(get_user(pte, ptep_user))) {
present = false;
break;
}
trace_kvm_mmu_paging_element(pte, walker->level);
if (!is_present_gpte(pte)) {
if (unlikely(!is_present_gpte(pte))) {
present = false;
break;
}
if (is_rsvd_bits_set(&vcpu->arch.mmu, pte, walker->level)) {
if (unlikely(is_rsvd_bits_set(&vcpu->arch.mmu, pte,
walker->level))) {
rsvd_fault = true;
break;
}
if (write_fault && !is_writable_pte(pte))
if (user_fault || is_write_protection(vcpu))
eperm = true;
if (unlikely(write_fault && !is_writable_pte(pte)
&& (user_fault || is_write_protection(vcpu))))
eperm = true;
if (user_fault && !(pte & PT_USER_MASK))
if (unlikely(user_fault && !(pte & PT_USER_MASK)))
eperm = true;
#if PTTYPE == 64
if (fetch_fault && (pte & PT64_NX_MASK))
if (unlikely(fetch_fault && (pte & PT64_NX_MASK)))
eperm = true;
#endif
if (!eperm && !rsvd_fault && !(pte & PT_ACCESSED_MASK)) {
if (!eperm && !rsvd_fault
&& unlikely(!(pte & PT_ACCESSED_MASK))) {
int ret;
trace_kvm_mmu_set_accessed_bit(table_gfn, index,
sizeof(pte));
@ -270,10 +272,10 @@ walk:
--walker->level;
}
if (!present || eperm || rsvd_fault)
if (unlikely(!present || eperm || rsvd_fault))
goto error;
if (write_fault && !is_dirty_gpte(pte)) {
if (write_fault && unlikely(!is_dirty_gpte(pte))) {
int ret;
trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));