Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756464Ab3CQPCr (ORCPT ); Sun, 17 Mar 2013 11:02:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11739 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756385Ab3CQPCo (ORCPT ); Sun, 17 Mar 2013 11:02:44 -0400 Date: Sun, 17 Mar 2013 17:02:39 +0200 From: Gleb Natapov To: Xiao Guangrong Cc: Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH 5/5] KVM: MMU: fast invalid all mmio sptes Message-ID: <20130317150239.GM11223@redhat.com> References: <51433D98.4050605@linux.vnet.ibm.com> <51433E71.2070107@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51433E71.2070107@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9363 Lines: 265 On Fri, Mar 15, 2013 at 11:29:53PM +0800, Xiao Guangrong wrote: > This patch tries to introduce a very simple and scale way to invalid all > mmio sptes - it need not walk any shadow pages and hold mmu-lock > > KVM maintains a global mmio invalid generation-number which is stored in > kvm->arch.mmio_invalid_gen and every mmio spte stores the current global > generation-number into his available bits when it is created > > When KVM need zap all mmio sptes, it just simply increase the global > generation-number. When guests do mmio access, KVM intercepts a MMIO #PF > then it walks the shadow page table and get the mmio spte. If the > generation-number on the spte does not equal the global generation-number, > it will go to the normal #PF handler to update the mmio spte > > Since 19 bits are used to store generation-number on mmio spte, the > generation-number can be round after 33554432 times. It is large enough > for nearly all most cases, but making the code be more strong, we zap all > shadow pages when the number is round > Very nice idea, but why drop Takuya patches instead of using kvm_mmu_zap_mmio_sptes() when generation number overflows. > Signed-off-by: Xiao Guangrong > --- > arch/x86/include/asm/kvm_host.h | 2 + > arch/x86/kvm/mmu.c | 61 +++++++++++++++++++++++++++++++++------ > arch/x86/kvm/mmutrace.h | 17 +++++++++++ > arch/x86/kvm/paging_tmpl.h | 7 +++- > arch/x86/kvm/vmx.c | 4 ++ > arch/x86/kvm/x86.c | 6 +-- > 6 files changed, 82 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index ef7f4a5..572398e 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -529,6 +529,7 @@ struct kvm_arch { > unsigned int n_requested_mmu_pages; > unsigned int n_max_mmu_pages; > unsigned int indirect_shadow_pages; > + unsigned int mmio_invalid_gen; Why invalid? Should be mmio_valid_gen or mmio_current_get. > struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES]; > /* > * Hash table of struct kvm_mmu_page. > @@ -765,6 +766,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot); > void kvm_mmu_write_protect_pt_masked(struct kvm *kvm, > struct kvm_memory_slot *slot, > gfn_t gfn_offset, unsigned long mask); > +void kvm_mmu_invalid_mmio_spte(struct kvm *kvm); Agree with Takuya that kvm_mmu_invalidate_mmio_sptes() is a better name. > void kvm_mmu_zap_all(struct kvm *kvm); > unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm); > void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages); > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 13626f4..7093a92 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -234,12 +234,13 @@ static unsigned int get_mmio_spte_generation(u64 spte) > static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn, > unsigned access) > { > - u64 mask = generation_mmio_spte_mask(0); > + unsigned int gen = ACCESS_ONCE(kvm->arch.mmio_invalid_gen); > + u64 mask = generation_mmio_spte_mask(gen); > > access &= ACC_WRITE_MASK | ACC_USER_MASK; > mask |= shadow_mmio_mask | access | gfn << PAGE_SHIFT; > > - trace_mark_mmio_spte(sptep, gfn, access, 0); > + trace_mark_mmio_spte(sptep, gfn, access, gen); > mmu_spte_set(sptep, mask); > } > > @@ -269,6 +270,34 @@ static bool set_mmio_spte(struct kvm *kvm, u64 *sptep, gfn_t gfn, > return false; > } > > +static bool check_mmio_spte(struct kvm *kvm, u64 spte) > +{ > + return get_mmio_spte_generation(spte) == > + ACCESS_ONCE(kvm->arch.mmio_invalid_gen); > +} > + > +/* > + * The caller should protect concurrent access on > + * kvm->arch.mmio_invalid_gen. Currently, it is used by > + * kvm_arch_commit_memory_region and protected by kvm->slots_lock. > + */ > +void kvm_mmu_invalid_mmio_spte(struct kvm *kvm) > +{ > + /* Ensure update memslot has been completed. */ > + smp_mb(); What barrier this one is paired with? > + > + trace_kvm_mmu_invalid_mmio_spte(kvm); Something wrong with indentation. > + > + /* > + * The very rare case: if the generation-number is round, > + * zap all shadow pages. > + */ > + if (unlikely(kvm->arch.mmio_invalid_gen++ == MAX_GEN)) { > + kvm->arch.mmio_invalid_gen = 0; > + return kvm_mmu_zap_all(kvm); > + } > +} > + > static inline u64 rsvd_bits(int s, int e) > { > return ((1ULL << (e - s + 1)) - 1) << s; > @@ -3183,9 +3212,12 @@ static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr) > } > > /* > - * If it is a real mmio page fault, return 1 and emulat the instruction > - * directly, return 0 to let CPU fault again on the address, -1 is > - * returned if bug is detected. > + * Return value: > + * 2: invalid spte is detected then let the real page fault path > + * update the mmio spte. > + * 1: it is a real mmio page fault, emulate the instruction directly. > + * 0: let CPU fault again on the address. > + * -1: bug is detected. > */ What about dropping spte and let guest re-fault instead of propagating new return value up the call chain. If this is slow lets at least define a enum with descriptive names. > int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct) > { > @@ -3200,6 +3232,9 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct) > gfn_t gfn = get_mmio_spte_gfn(spte); > unsigned access = get_mmio_spte_access(spte); > > + if (unlikely(!check_mmio_spte(vcpu->kvm, spte))) > + return 2; > + > if (direct) > addr = 0; > > @@ -3241,8 +3276,12 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva, > > pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code); > > - if (unlikely(error_code & PFERR_RSVD_MASK)) > - return handle_mmio_page_fault(vcpu, gva, error_code, true); > + if (unlikely(error_code & PFERR_RSVD_MASK)) { > + r = handle_mmio_page_fault(vcpu, gva, error_code, true); > + > + if (likely(r != 2)) > + return r; > + } > > r = mmu_topup_memory_caches(vcpu); > if (r) > @@ -3318,8 +3357,12 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code, > ASSERT(vcpu); > ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa)); > > - if (unlikely(error_code & PFERR_RSVD_MASK)) > - return handle_mmio_page_fault(vcpu, gpa, error_code, true); > + if (unlikely(error_code & PFERR_RSVD_MASK)) { > + r = handle_mmio_page_fault(vcpu, gpa, error_code, true); > + > + if (likely(r != 2)) > + return r; > + } > > r = mmu_topup_memory_caches(vcpu); > if (r) > diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h > index f5b62a7..811254c 100644 > --- a/arch/x86/kvm/mmutrace.h > +++ b/arch/x86/kvm/mmutrace.h > @@ -276,6 +276,23 @@ TRACE_EVENT( > __spte_satisfied(old_spte), __spte_satisfied(new_spte) > ) > ); > + > +TRACE_EVENT( > + kvm_mmu_invalid_mmio_spte, > + TP_PROTO(struct kvm *kvm), > + TP_ARGS(kvm), > + > + TP_STRUCT__entry( > + __field(unsigned int, mmio_invalid_gen) > + ), > + > + TP_fast_assign( > + __entry->mmio_invalid_gen = kvm->arch.mmio_invalid_gen; > + ), > + > + TP_printk("mmio_invalid_gen %x", __entry->mmio_invalid_gen > + ) > +); > #endif /* _TRACE_KVMMMU_H */ > > #undef TRACE_INCLUDE_PATH > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > index 2c48e5f..c81f949 100644 > --- a/arch/x86/kvm/paging_tmpl.h > +++ b/arch/x86/kvm/paging_tmpl.h > @@ -552,9 +552,12 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, > > pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); > > - if (unlikely(error_code & PFERR_RSVD_MASK)) > - return handle_mmio_page_fault(vcpu, addr, error_code, > + if (unlikely(error_code & PFERR_RSVD_MASK)) { > + r = handle_mmio_page_fault(vcpu, addr, error_code, > mmu_is_nested(vcpu)); > + if (likely(r != 2)) > + return r; > + }; > > r = mmu_topup_memory_caches(vcpu); > if (r) > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 54fdb76..ca8e9a3 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -5159,6 +5159,10 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu) > if (likely(ret == 1)) > return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) == > EMULATE_DONE; > + > + if (unlikely(ret == 2)) > + return kvm_mmu_page_fault(vcpu, gpa, 0, NULL, 0); > + > if (unlikely(!ret)) > return 1; > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 81fb3c3..5b6d2a0 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6996,10 +6996,8 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, > * If memory slot is created, or moved, we need to clear all > * mmio sptes. > */ > - if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) { > - kvm_mmu_zap_all(kvm); > - kvm_reload_remote_mmus(kvm); > - } > + if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) > + kvm_mmu_invalid_mmio_spte(kvm); > } > > void kvm_arch_flush_shadow_all(struct kvm *kvm) > -- > 1.7.7.6 -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/