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[2620:137:e000::1:20]) by mx.google.com with ESMTP id cw5-20020a170906478500b007ae832c0b6bsi2656203ejc.508.2022.11.08.20.46.43; Tue, 08 Nov 2022 20:47:31 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=fAFMKNHw; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229528AbiKIESp (ORCPT + 94 others); Tue, 8 Nov 2022 23:18:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229488AbiKIESj (ORCPT ); Tue, 8 Nov 2022 23:18:39 -0500 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E090DCE0D; Tue, 8 Nov 2022 20:18:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1667967518; x=1699503518; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=zBd0WQHBdR3NPWzJNZfDs4ykgtZDGmbYGFzZ8L5rmrk=; b=fAFMKNHw15zWY78fsi5/fwnE2M1yhsQ9J7CDxVMD5BvjXLJhc/ocnGSi X+ndghdg/x7VQW9hQIedjzLSTy89lzq40zSrBqfaG3yhQLz8tHJVA8Z5c C4gWiBrF+EmwnYsa8lN8DU8vMkhUHuKamA1K8LeDkPOd3qV61VeQSaQeY N9NBhpyZ2XlbPCiBCmpihYLX7QswAj/1NPihyCeLNaGWLyiKl28o/T9AQ h2stzUaNDMiCaECgXCsQlgr1LMQtMA/kuHMhfMLHwWh6erY8dDuJrmOou GFmXR57iKdBnHyHXGJG5x0Hxka16WZxiL5Hc7cLKo41nV2vpLPTV3SP91 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10525"; a="373029544" X-IronPort-AV: E=Sophos;i="5.96,149,1665471600"; d="scan'208";a="373029544" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Nov 2022 20:18:36 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10525"; a="614533677" X-IronPort-AV: E=Sophos;i="5.96,149,1665471600"; d="scan'208";a="614533677" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.193.75]) by orsmga006.jf.intel.com with ESMTP; 08 Nov 2022 20:18:25 -0800 Date: Wed, 9 Nov 2022 12:13:58 +0800 From: Chao Peng To: Yuan Yao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , tabba@google.com, Michael Roth , mhocko@suse.com, Muchun Song , wei.w.wang@intel.com Subject: Re: [PATCH v9 6/8] KVM: Update lpage info when private/shared memory are mixed Message-ID: <20221109041358.GA118963@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221025151344.3784230-1-chao.p.peng@linux.intel.com> <20221025151344.3784230-7-chao.p.peng@linux.intel.com> <20221108120805.kize74qgzsmarze5@yy-desk-7060> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221108120805.kize74qgzsmarze5@yy-desk-7060> X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 08, 2022 at 08:08:05PM +0800, Yuan Yao wrote: > On Tue, Oct 25, 2022 at 11:13:42PM +0800, Chao Peng wrote: > > When private/shared memory are mixed in a large page, the lpage_info may > > not be accurate and should be updated with this mixed info. A large page > > has mixed pages can't be really mapped as large page since its > > private/shared pages are from different physical memory. > > > > Update lpage_info when private/shared memory attribute is changed. If > > both private and shared pages are within a large page region, it can't > > be mapped as large page. It's a bit challenge to track the mixed > > info in a 'count' like variable, this patch instead reserves a bit in > > 'disallow_lpage' to indicate a large page has mixed private/share pages. > > > > Signed-off-by: Chao Peng > > --- > > arch/x86/include/asm/kvm_host.h | 8 +++ > > arch/x86/kvm/mmu/mmu.c | 112 +++++++++++++++++++++++++++++++- > > arch/x86/kvm/x86.c | 2 + > > include/linux/kvm_host.h | 19 ++++++ > > virt/kvm/kvm_main.c | 16 +++-- > > 5 files changed, 152 insertions(+), 5 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 7551b6f9c31c..db811a54e3fd 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -37,6 +37,7 @@ > > #include > > > > #define __KVM_HAVE_ARCH_VCPU_DEBUGFS > > +#define __KVM_HAVE_ARCH_UPDATE_MEM_ATTR > > > > #define KVM_MAX_VCPUS 1024 > > > > @@ -952,6 +953,13 @@ struct kvm_vcpu_arch { > > #endif > > }; > > > > +/* > > + * Use a bit in disallow_lpage to indicate private/shared pages mixed at the > > + * level. The remaining bits are used as a reference count. > > + */ > > +#define KVM_LPAGE_PRIVATE_SHARED_MIXED (1U << 31) > > +#define KVM_LPAGE_COUNT_MAX ((1U << 31) - 1) > > + > > struct kvm_lpage_info { > > int disallow_lpage; > > }; > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index 33b1aec44fb8..67a9823a8c35 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -762,11 +762,16 @@ static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot, > > { > > struct kvm_lpage_info *linfo; > > int i; > > + int disallow_count; > > > > for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) { > > linfo = lpage_info_slot(gfn, slot, i); > > + > > + disallow_count = linfo->disallow_lpage & KVM_LPAGE_COUNT_MAX; > > + WARN_ON(disallow_count + count < 0 || > > + disallow_count > KVM_LPAGE_COUNT_MAX - count); > > + > > linfo->disallow_lpage += count; > > - WARN_ON(linfo->disallow_lpage < 0); > > } > > } > > > > @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm) > > if (kvm->arch.nx_lpage_recovery_thread) > > kthread_stop(kvm->arch.nx_lpage_recovery_thread); > > } > > + > > +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo) > > +{ > > + return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED; > > +} > > + > > +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed) > > +{ > > + if (mixed) > > + linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED; > > + else > > + linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED; > > +} > > + > > +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > + XA_STATE(xas, &kvm->mem_attr_array, start); > > + gfn_t gfn = start; > > + void *entry; > > + bool shared = attr == KVM_MEM_ATTR_SHARED; > > + bool mixed = false; > > + > > + rcu_read_lock(); > > + entry = xas_load(&xas); > > + while (gfn < end) { > > + if (xas_retry(&xas, entry)) > > + continue; > > + > > + KVM_BUG_ON(gfn != xas.xa_index, kvm); > > + > > + if ((entry && !shared) || (!entry && shared)) { > > + mixed = true; > > + goto out; > > + } > > + > > + entry = xas_next(&xas); > > + gfn++; > > + } > > +out: > > + rcu_read_unlock(); > > + return mixed; > > +} > > + > > +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot, > > + int level, unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > + unsigned long gfn; > > + void *entry; > > + > > + if (level == PG_LEVEL_2M) > > + return mem_attr_is_mixed_2m(kvm, attr, start, end); > > + > > + entry = xa_load(&kvm->mem_attr_array, start); > > + for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) { > > + if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1))) > > + return true; > > + if (xa_load(&kvm->mem_attr_array, gfn) != entry) > > + return true; > > + } > > + return false; > > +} > > + > > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot, > > + unsigned int attr, gfn_t start, gfn_t end) > > +{ > > + > > + unsigned long lpage_start, lpage_end; > > + unsigned long gfn, pages, mask; > > + int level; > > + > > + WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)), > > + "Unsupported mem attribute.\n"); > > + > > + /* > > + * The sequence matters here: we update the higher level basing on the > > + * lower level's scanning result. > > + */ > > + for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { > > + pages = KVM_PAGES_PER_HPAGE(level); > > + mask = ~(pages - 1); > > + lpage_start = max(start & mask, slot->base_gfn); > > + lpage_end = (end - 1) & mask; > > + > > + /* > > + * We only need to scan the head and tail page, for middle pages > > + * we know they are not mixed. > > + */ > > + linfo_update_mixed(lpage_info_slot(lpage_start, slot, level), > > + mem_attr_is_mixed(kvm, slot, level, attr, > > + lpage_start, start)); > > Looks only query the lpage_start, start is not enough: > > A and B are private gfns from same lpage_start as below, A > B : > lpage_start > |---------A > |----B > > Convert A to shared, this makes the upper 2M page to MIX. > Convert B to shared, this also makes the upper 2M page to MIX. > Convert B to private, this makes the upper 2M page to Non-MIX, but > it's incorrect, due to A is shared. In previous versions this is actually "lpage_start, lpage_start + pages", e.g. covers the whole large page. While fixing another issue[*] in v8 this was wrongly changed to "lpage_start, start", at that time I made an assumption that "end > lpage_start + pages" so the remaining scanning in the same large page is useless if we know what attribute we will set, this is definitely not true though. [*] https://lore.kernel.org/linux-mm/20220930085914.GA2799703@chaop.bj.intel.com/ Thanks, Chao > > Same to tail case. > > > + > > + if (lpage_start == lpage_end) > > + return; > > + > > + for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages) > > + linfo_update_mixed(lpage_info_slot(gfn, slot, level), > > + false); > > + > > + linfo_update_mixed(lpage_info_slot(lpage_end, slot, level), > > + mem_attr_is_mixed(kvm, slot, level, attr, > > + end, lpage_end + pages)); > > + } > > +} > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 02ad31f46dd7..4276ca73bd7b 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -12563,6 +12563,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm, > > if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1)) > > linfo[lpages - 1].disallow_lpage = 1; > > ugfn = slot->userspace_addr >> PAGE_SHIFT; > > + if (kvm_slot_can_be_private(slot)) > > + ugfn |= slot->restricted_offset >> PAGE_SHIFT; > > /* > > * If the gfn and userspace address are not aligned wrt each > > * other, disable large page support for this slot. > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 4ce98fa0153c..6ce36065532c 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -2284,4 +2284,23 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr) > > /* Max number of entries allowed for each kvm dirty ring */ > > #define KVM_DIRTY_RING_MAX_ENTRIES 65536 > > > > +#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM > > + > > +#define KVM_MEM_ATTR_SHARED 0x0001 > > +#define KVM_MEM_ATTR_PRIVATE 0x0002 > > + > > +#ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR > > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot, > > + unsigned int attr, gfn_t start, gfn_t end); > > +#else > > +static inline void kvm_arch_update_mem_attr(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > +} > > +#endif > > + > > +#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */ > > + > > #endif > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index fc3835826ace..13a37b4d9e97 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -939,7 +939,8 @@ static int kvm_init_mmu_notifier(struct kvm *kvm) > > > > #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM > > > > -static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end) > > +static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end, > > + unsigned int attr) > > { > > struct kvm_gfn_range gfn_range; > > struct kvm_memory_slot *slot; > > @@ -963,6 +964,7 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end) > > gfn_range.slot = slot; > > > > r |= kvm_unmap_gfn_range(kvm, &gfn_range); > > + kvm_arch_update_mem_attr(kvm, slot, attr, start, end); > > } > > } > > > > @@ -970,7 +972,6 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end) > > kvm_flush_remote_tlbs(kvm); > > } > > > > -#define KVM_MEM_ATTR_SHARED 0x0001 > > static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > > bool is_private) > > { > > @@ -979,6 +980,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > > void *entry; > > int idx; > > int r = 0; > > + unsigned int attr; > > > > if (size == 0 || gpa + size < gpa) > > return -EINVAL; > > @@ -992,7 +994,13 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > > * Guest memory defaults to private, kvm->mem_attr_array only stores > > * shared memory. > > */ > > - entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED); > > + if (is_private) { > > + attr = KVM_MEM_ATTR_PRIVATE; > > + entry = NULL; > > + } else { > > + attr = KVM_MEM_ATTR_SHARED; > > + entry = xa_mk_value(KVM_MEM_ATTR_SHARED); > > + } > > > > idx = srcu_read_lock(&kvm->srcu); > > KVM_MMU_LOCK(kvm); > > @@ -1005,7 +1013,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > > goto err; > > } > > > > - kvm_unmap_mem_range(kvm, start, end); > > + kvm_unmap_mem_range(kvm, start, end, attr); > > > > goto ret; > > err: > > -- > > 2.25.1 > >