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    SubjectRe: [PATCH 07/11] KVM: MMU: fast prefetch spte on invlpg path
    On Tue, Aug 16, 2011 at 02:44:42PM +0800, Xiao Guangrong wrote:
    > Fast prefetch spte for the unsync shadow page on invlpg path
    >
    > Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    > ---
    > arch/x86/include/asm/kvm_host.h | 4 +---
    > arch/x86/kvm/mmu.c | 38 +++++++++++++++-----------------------
    > arch/x86/kvm/paging_tmpl.h | 30 ++++++++++++++++++------------
    > arch/x86/kvm/x86.c | 4 ++--
    > 4 files changed, 36 insertions(+), 40 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > index 58ea3a7..927ba73 100644
    > --- a/arch/x86/include/asm/kvm_host.h
    > +++ b/arch/x86/include/asm/kvm_host.h
    > @@ -460,7 +460,6 @@ struct kvm_arch {
    > unsigned int n_requested_mmu_pages;
    > unsigned int n_max_mmu_pages;
    > unsigned int indirect_shadow_pages;
    > - atomic_t invlpg_counter;
    > struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
    > /*
    > * Hash table of struct kvm_mmu_page.
    > @@ -754,8 +753,7 @@ int fx_init(struct kvm_vcpu *vcpu);
    >
    > void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
    > void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    > - const u8 *new, int bytes,
    > - bool guest_initiated);
    > + const u8 *new, int bytes);
    > int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
    > int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
    > void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
    > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    > index ed3e778..f6de2fc 100644
    > --- a/arch/x86/kvm/mmu.c
    > +++ b/arch/x86/kvm/mmu.c
    > @@ -3530,8 +3530,7 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
    > }
    >
    > void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    > - const u8 *new, int bytes,
    > - bool guest_initiated)
    > + const u8 *new, int bytes)
    > {
    > gfn_t gfn = gpa >> PAGE_SHIFT;
    > union kvm_mmu_page_role mask = { .word = 0 };
    > @@ -3540,7 +3539,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    > LIST_HEAD(invalid_list);
    > u64 entry, gentry, *spte;
    > unsigned pte_size, page_offset, misaligned, quadrant, offset;
    > - int level, npte, invlpg_counter, r, flooded = 0;
    > + int level, npte, r, flooded = 0;
    > bool remote_flush, local_flush, zap_page;
    >
    > /*
    > @@ -3555,19 +3554,16 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    >
    > pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
    >
    > - invlpg_counter = atomic_read(&vcpu->kvm->arch.invlpg_counter);
    > -
    > /*
    > * Assume that the pte write on a page table of the same type
    > * as the current vcpu paging mode since we update the sptes only
    > * when they have the same mode.
    > */
    > - if ((is_pae(vcpu) && bytes == 4) || !new) {
    > + if (is_pae(vcpu) && bytes == 4) {
    > /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
    > - if (is_pae(vcpu)) {
    > - gpa &= ~(gpa_t)7;
    > - bytes = 8;
    > - }
    > + gpa &= ~(gpa_t)7;
    > + bytes = 8;
    > +
    > r = kvm_read_guest(vcpu->kvm, gpa, &gentry, min(bytes, 8));
    > if (r)
    > gentry = 0;
    > @@ -3593,22 +3589,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    > */
    > mmu_topup_memory_caches(vcpu);
    > spin_lock(&vcpu->kvm->mmu_lock);
    > - if (atomic_read(&vcpu->kvm->arch.invlpg_counter) != invlpg_counter)
    > - gentry = 0;
    > kvm_mmu_free_some_pages(vcpu);
    > ++vcpu->kvm->stat.mmu_pte_write;
    > trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
    > - if (guest_initiated) {
    > - if (gfn == vcpu->arch.last_pt_write_gfn
    > - && !last_updated_pte_accessed(vcpu)) {
    > - ++vcpu->arch.last_pt_write_count;
    > - if (vcpu->arch.last_pt_write_count >= 3)
    > - flooded = 1;
    > - } else {
    > - vcpu->arch.last_pt_write_gfn = gfn;
    > - vcpu->arch.last_pt_write_count = 1;
    > - vcpu->arch.last_pte_updated = NULL;
    > - }
    > + if (gfn == vcpu->arch.last_pt_write_gfn
    > + && !last_updated_pte_accessed(vcpu)) {
    > + ++vcpu->arch.last_pt_write_count;
    > + if (vcpu->arch.last_pt_write_count >= 3)
    > + flooded = 1;
    > + } else {
    > + vcpu->arch.last_pt_write_gfn = gfn;
    > + vcpu->arch.last_pt_write_count = 1;
    > + vcpu->arch.last_pte_updated = NULL;
    > }
    >
    > mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
    > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
    > index 7862c05..bdc2241 100644
    > --- a/arch/x86/kvm/paging_tmpl.h
    > +++ b/arch/x86/kvm/paging_tmpl.h
    > @@ -670,20 +670,27 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
    > {
    > struct kvm_shadow_walk_iterator iterator;
    > struct kvm_mmu_page *sp;
    > - gpa_t pte_gpa = -1;
    > int level;
    > u64 *sptep;
    >
    > vcpu_clear_mmio_info(vcpu, gva);
    >
    > - spin_lock(&vcpu->kvm->mmu_lock);
    > + /*
    > + * No need to check return value here, rmap_can_add() can
    > + * help us to skip pte prefetch later.
    > + */
    > + mmu_topup_memory_caches(vcpu);
    >
    > + spin_lock(&vcpu->kvm->mmu_lock);
    > for_each_shadow_entry(vcpu, gva, iterator) {
    > level = iterator.level;
    > sptep = iterator.sptep;
    >
    > sp = page_header(__pa(sptep));
    > if (is_last_spte(*sptep, level)) {
    > + pt_element_t gpte;
    > + gpa_t pte_gpa;
    > +
    > if (!sp->unsync)
    > break;
    >
    > @@ -692,22 +699,21 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
    >
    > if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
    > kvm_flush_remote_tlbs(vcpu->kvm);
    > +
    > + if (rmap_can_add(vcpu))
    > + break;

    if (!rmap_can_add(vcpu))
    break;

    ?

    > +
    > + if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte,
    > + sizeof(pt_element_t)))
    > + break;
    > +
    > + FNAME(update_pte)(vcpu, sp, sptep, &gpte);
    > }
    >
    > if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
    > break;



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