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Date: Fri, 8 Feb 2013 19:35:34 -0200
From: Marcelo Tosatti <mtosatti@...hat.com>
To: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc: Gleb Natapov <gleb@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 1/5] KVM: MMU: introduce mmu_spte_establish
On Tue, Feb 05, 2013 at 04:53:19PM +0800, Xiao Guangrong wrote:
> There is little different between walking parent pte and walking ramp:
> all spte in rmap must be present but this is not true on parent pte list,
> in kvm_mmu_alloc_page, we always link the parent list before set the spte
> to present
>
> This patch introduce mmu_spte_establish which set the spte before linking
> it to parent list to eliminates the different then it is possible to unify
> the code of walking pte list
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> ---
> arch/x86/kvm/mmu.c | 81 ++++++++++++++++++++++---------------------
> arch/x86/kvm/paging_tmpl.h | 16 ++++-----
> 2 files changed, 48 insertions(+), 49 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 8041454..68d4d5f 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1482,9 +1482,6 @@ static unsigned kvm_page_table_hashfn(gfn_t gfn)
> static void mmu_page_add_parent_pte(struct kvm_vcpu *vcpu,
> struct kvm_mmu_page *sp, u64 *parent_pte)
> {
> - if (!parent_pte)
> - return;
> -
> pte_list_add(vcpu, parent_pte, &sp->parent_ptes);
> }
>
> @@ -1502,7 +1499,7 @@ static void drop_parent_pte(struct kvm_mmu_page *sp,
> }
>
> static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
> - u64 *parent_pte, int direct)
> + int direct)
> {
> struct kvm_mmu_page *sp;
> sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
> @@ -1512,7 +1509,6 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
> set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
> list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
> sp->parent_ptes = 0;
> - mmu_page_add_parent_pte(vcpu, sp, parent_pte);
> kvm_mod_used_mmu_pages(vcpu->kvm, +1);
> return sp;
> }
> @@ -1845,8 +1841,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> gva_t gaddr,
> unsigned level,
> int direct,
> - unsigned access,
> - u64 *parent_pte)
> + unsigned access)
> {
> union kvm_mmu_page_role role;
> unsigned quadrant;
> @@ -1876,19 +1871,15 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> if (sp->unsync && kvm_sync_page_transient(vcpu, sp))
> break;
>
> - mmu_page_add_parent_pte(vcpu, sp, parent_pte);
> - if (sp->unsync_children) {
> + if (sp->unsync_children)
> kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
> - kvm_mmu_mark_parents_unsync(sp);
> - } else if (sp->unsync)
> - kvm_mmu_mark_parents_unsync(sp);
>
> __clear_sp_write_flooding_count(sp);
> trace_kvm_mmu_get_page(sp, false);
> return sp;
> }
> ++vcpu->kvm->stat.mmu_cache_miss;
> - sp = kvm_mmu_alloc_page(vcpu, parent_pte, direct);
> + sp = kvm_mmu_alloc_page(vcpu, direct);
> if (!sp)
> return sp;
> sp->gfn = gfn;
> @@ -1908,6 +1899,35 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> return sp;
> }
>
> +static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp)
> +{
> + u64 spte;
> +
> + spte = __pa(sp->spt) | PT_PRESENT_MASK | PT_WRITABLE_MASK |
> + shadow_user_mask | shadow_x_mask | shadow_accessed_mask;
> +
> + mmu_spte_set(sptep, spte);
> +}
> +
> +static struct kvm_mmu_page *
> +mmu_spte_establish(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn, gva_t gaddr,
> + unsigned level, int direct, unsigned access)
> +{
> + struct kvm_mmu_page *sp;
> +
> + WARN_ON(is_shadow_present_pte(*spte));
> +
> + sp = kvm_mmu_get_page(vcpu, gfn, gaddr, level, direct, access);
> +
> + link_shadow_page(spte, sp);
> + mmu_page_add_parent_pte(vcpu, sp, spte);
> +
> + if (sp->unsync_children || sp->unsync)
> + kvm_mmu_mark_parents_unsync(sp);
> +
> + return sp;
> +}
> +
> static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator,
> struct kvm_vcpu *vcpu, u64 addr)
> {
> @@ -1957,16 +1977,6 @@ static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
> return __shadow_walk_next(iterator, *iterator->sptep);
> }
>
> -static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp)
> -{
> - u64 spte;
> -
> - spte = __pa(sp->spt) | PT_PRESENT_MASK | PT_WRITABLE_MASK |
> - shadow_user_mask | shadow_x_mask | shadow_accessed_mask;
> -
> - mmu_spte_set(sptep, spte);
> -}
> -
> static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> unsigned direct_access)
> {
> @@ -2023,11 +2033,6 @@ static void kvm_mmu_page_unlink_children(struct kvm *kvm,
> mmu_page_zap_pte(kvm, sp, sp->spt + i);
> }
>
> -static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
> -{
> - mmu_page_remove_parent_pte(sp, parent_pte);
> -}
> -
> static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
> {
> u64 *sptep;
> @@ -2582,9 +2587,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
> bool prefault)
> {
> struct kvm_shadow_walk_iterator iterator;
> - struct kvm_mmu_page *sp;
> int emulate = 0;
> - gfn_t pseudo_gfn;
>
> for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
> if (iterator.level == level) {
> @@ -2602,12 +2605,11 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
> u64 base_addr = iterator.addr;
>
> base_addr &= PT64_LVL_ADDR_MASK(iterator.level);
> - pseudo_gfn = base_addr >> PAGE_SHIFT;
> - sp = kvm_mmu_get_page(vcpu, pseudo_gfn, iterator.addr,
> - iterator.level - 1,
> - 1, ACC_ALL, iterator.sptep);
> + mmu_spte_establish(vcpu, iterator.sptep,
> + gpa_to_gfn(base_addr),
> + iterator.addr, iterator.level - 1,
> + 1, ACC_ALL);
>
> - link_shadow_page(iterator.sptep, sp);
> }
> }
> return emulate;
> @@ -2926,7 +2928,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
> spin_lock(&vcpu->kvm->mmu_lock);
> kvm_mmu_free_some_pages(vcpu);
> sp = kvm_mmu_get_page(vcpu, 0, 0, PT64_ROOT_LEVEL,
> - 1, ACC_ALL, NULL);
> + 1, ACC_ALL);
> ++sp->root_count;
> spin_unlock(&vcpu->kvm->mmu_lock);
> vcpu->arch.mmu.root_hpa = __pa(sp->spt);
> @@ -2939,8 +2941,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
> kvm_mmu_free_some_pages(vcpu);
> sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT),
> i << 30,
> - PT32_ROOT_LEVEL, 1, ACC_ALL,
> - NULL);
> + PT32_ROOT_LEVEL, 1, ACC_ALL);
> root = __pa(sp->spt);
> ++sp->root_count;
> spin_unlock(&vcpu->kvm->mmu_lock);
> @@ -2977,7 +2978,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> spin_lock(&vcpu->kvm->mmu_lock);
> kvm_mmu_free_some_pages(vcpu);
> sp = kvm_mmu_get_page(vcpu, root_gfn, 0, PT64_ROOT_LEVEL,
> - 0, ACC_ALL, NULL);
> + 0, ACC_ALL);
> root = __pa(sp->spt);
> ++sp->root_count;
> spin_unlock(&vcpu->kvm->mmu_lock);
> @@ -3012,7 +3013,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> kvm_mmu_free_some_pages(vcpu);
> sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
> PT32_ROOT_LEVEL, 0,
> - ACC_ALL, NULL);
> + ACC_ALL);
> root = __pa(sp->spt);
> ++sp->root_count;
> spin_unlock(&vcpu->kvm->mmu_lock);
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 105dd5b..3605ff7 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -434,8 +434,9 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
> sp = NULL;
> if (!is_shadow_present_pte(*it.sptep)) {
> table_gfn = gw->table_gfn[it.level - 2];
> - sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
> - false, access, it.sptep);
> + sp = mmu_spte_establish(vcpu, it.sptep, table_gfn,
> + addr, it.level-1, false,
> + access);
> }
>
> /*
> @@ -444,9 +445,6 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
> */
> if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
> goto out_gpte_changed;
> -
> - if (sp)
> - link_shadow_page(it.sptep, sp);
> }
>
> for (;
> @@ -464,9 +462,8 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>
> direct_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
>
> - sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1,
> - true, direct_access, it.sptep);
> - link_shadow_page(it.sptep, sp);
> + mmu_spte_establish(vcpu, it.sptep, direct_gfn, addr,
+ it.level-1, true, direct_access);
> }
>
> clear_sp_write_flooding_count(it.sptep);
> @@ -478,7 +475,8 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>
> out_gpte_changed:
> if (sp)
> - kvm_mmu_put_page(sp, it.sptep);
> + drop_parent_pte(sp, it.sptep);
> +
Unclear why TLB flushing not necessary here (entry it could have been
added to remote CPU's TLB since it has been linked).
--
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