From 6e2ca7d1802bf8ed9908435e34daa116662e7790 Mon Sep 17 00:00:00 2001 From: Takuya Yoshikawa Date: Fri, 22 Apr 2011 00:34:44 +0900 Subject: [PATCH] KVM: MMU: Optimize guest page table walk This patch optimizes the guest page table walk by using get_user() instead of copy_from_user(). With this patch applied, paging64_walk_addr_generic() has become about 0.5us to 1.0us faster on my Phenom II machine with NPT on. Signed-off-by: Takuya Yoshikawa Signed-off-by: Avi Kivity --- arch/x86/kvm/paging_tmpl.h | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 1b6899088f97..a32a1c809149 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -123,6 +123,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, gva_t addr, u32 access) { pt_element_t pte; + pt_element_t __user *ptep_user; gfn_t table_gfn; unsigned index, pt_access, uninitialized_var(pte_access); gpa_t pte_gpa; @@ -158,6 +159,9 @@ walk: pt_access = ACC_ALL; for (;;) { + gfn_t real_gfn; + unsigned long host_addr; + index = PT_INDEX(addr, walker->level); table_gfn = gpte_to_gfn(pte); @@ -166,9 +170,22 @@ walk: walker->table_gfn[walker->level - 1] = table_gfn; walker->pte_gpa[walker->level - 1] = pte_gpa; - if (kvm_read_guest_page_mmu(vcpu, mmu, table_gfn, &pte, - offset, sizeof(pte), - PFERR_USER_MASK|PFERR_WRITE_MASK)) { + real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn), + PFERR_USER_MASK|PFERR_WRITE_MASK); + if (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)) { + present = false; + break; + } + + ptep_user = (pt_element_t __user *)((void *)host_addr + offset); + if (get_user(pte, ptep_user)) { present = false; break; }