On 2011-04-21 17:34, Takuya Yoshikawa wrote: > From: Takuya Yoshikawa <[email protected]> > > 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 <[email protected]> > --- > arch/x86/kvm/paging_tmpl.h | 23 ++++++++++++++++++++--- > 1 files changed, 20 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > index 74f8567..825d953 100644 > --- a/arch/x86/kvm/paging_tmpl.h > +++ b/arch/x86/kvm/paging_tmpl.h > @@ -117,6 +117,7 @@ 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; > @@ -152,6 +153,9 @@ 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); > @@ -160,9 +164,22 @@ 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)) { ^^^^^^^^^^^^ This doesn't work for x86-32: pte is 64 bit, but get_user is only defined up to 32 bit on that platform.
Avi, what's your 32-bit buildbot doing? :) Jan
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