From patchwork Tue May 18 17:34:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Gardon X-Patchwork-Id: 12265249 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F3DFC43470 for ; Tue, 18 May 2021 17:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00323611AC for ; Tue, 18 May 2021 17:34:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351210AbhERRfy (ORCPT ); Tue, 18 May 2021 13:35:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41052 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351202AbhERRfu (ORCPT ); Tue, 18 May 2021 13:35:50 -0400 Received: from mail-qk1-x749.google.com (mail-qk1-x749.google.com [IPv6:2607:f8b0:4864:20::749]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECB17C06175F for ; Tue, 18 May 2021 10:34:31 -0700 (PDT) Received: by mail-qk1-x749.google.com with SMTP id 140-20020a3704920000b02903a568b50545so2015143qke.7 for ; Tue, 18 May 2021 10:34:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=QJBRdiNT50y6CWenT8iHGZ+jatWGFL5n8aWtdmK//io=; b=lq+642t/uIN+3l8/YXQdQ9VpERXKH/FAKZ1CnqHdfk7zw8dw3Om/dUBR3SYDjfA0mT QJCesbCHigRxleDQ6xFaX0f8i1b88osHnoE1mlgc2s0w52TJvgPWBKYI+8e4jTI6Y2qX +wtP+1qhfBMSNytwthMAph2umI4nVKkGrXdc68MF9/VO65PbcK6MNKkny34eWznp26UT QTCYBsEtNaHnjwN1WqqFqvd02QRAfoWgi4+mloYhH034hSwVVD/41SpDz82HfkxZUsTj LorhErhgAW9deu8ZqCeGImJ9Dfj7fz38r0u21ma5t80GpijY5/F6aHCochR+iWrr/g9D Ahjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=QJBRdiNT50y6CWenT8iHGZ+jatWGFL5n8aWtdmK//io=; b=jCWLGa17DoFULkViHTWtPiYy0WSLSO9X70xK1mU57qqoh3Jdy2b8jajtqcC/CPIN/8 YqeHQU/r5JrHIOPXv5G61Mz70pIn/W4yv71IlsD5TcEaR5oH5nd1DJqMuERguWqUqWlS J4F44cK1z+SEIrgVjgIby+mcg915r9fpDWrLPRi4XtHgHIDkzePHY1K1dyfqnYtEBg2n CLDjDV5DPkwX2uLPm171/bZUTmTcZWXWcEYMmbJ1sC4PElJ4S4EnvRug982/0W3hZzEg Ss1G/TzPUniq9PO0MrOYODezQaUBmOX1QBArXgk81MrgJoNlAuphmP2IstRJRZmofKA+ 75SQ== X-Gm-Message-State: AOAM530MrdNMmZ2c/aAHUhMdSRWS30z11rXTbTdyuO6ckh+9NnCYoW2A m/wLITy0MX+70CN72eJTaa+9+TG1GDBo X-Google-Smtp-Source: ABdhPJxlZBvsJ7tEWJAysMi9ycSI3V6Lv90wDn44kMX/vfhOOjh0C8HqUirDFz7+ImKy1PFaGMwoGIO3Zt5C X-Received: from bgardon.sea.corp.google.com ([2620:15c:100:202:2715:2de:868e:9db7]) (user=bgardon job=sendgmr) by 2002:a0c:8e49:: with SMTP id w9mr6721541qvb.35.1621359271150; Tue, 18 May 2021 10:34:31 -0700 (PDT) Date: Tue, 18 May 2021 10:34:14 -0700 In-Reply-To: <20210518173414.450044-1-bgardon@google.com> Message-Id: <20210518173414.450044-8-bgardon@google.com> Mime-Version: 1.0 References: <20210518173414.450044-1-bgardon@google.com> X-Mailer: git-send-email 2.31.1.751.gd2f1c929bd-goog Subject: [PATCH v5 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps From: Ben Gardon To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Peter Xu , Sean Christopherson , Peter Shier , Yulei Zhang , Wanpeng Li , Xiao Guangrong , Kai Huang , Keqian Zhu , David Hildenbrand , Ben Gardon Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org If the TDP MMU is in use, wait to allocate the rmaps until the shadow MMU is actually used. (i.e. a nested VM is launched.) This saves memory equal to 0.2% of guest memory in cases where the TDP MMU is used and there are no nested guests involved. Signed-off-by: Ben Gardon --- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/mmu.h | 7 ++++- arch/x86/kvm/mmu/mmu.c | 14 +++++++--- arch/x86/kvm/mmu/tdp_mmu.c | 6 +++-- arch/x86/kvm/mmu/tdp_mmu.h | 4 +-- arch/x86/kvm/x86.c | 46 +++++++++++++++++++++++++++++++++ 6 files changed, 71 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index fc75ed49bfee..7b65f82ade1c 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1868,4 +1868,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu) int kvm_cpu_dirty_log_size(void); +int alloc_all_memslots_rmaps(struct kvm *kvm); + #endif /* _ASM_X86_KVM_HOST_H */ diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index af09c47b1aa2..e987c9af82b6 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -234,7 +234,12 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm); static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) { - return kvm->arch.memslots_have_rmaps; + /* + * Ensure that threads reading memslots_have_rmaps in various + * lock contexts see the value before trying to dereference + * the memslot rmap pointers. + */ + return smp_load_acquire(&kvm->arch.memslots_have_rmaps); } #endif diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 1e0daabc83ca..2ac7bec515a1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3294,6 +3294,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) } } + r = alloc_all_memslots_rmaps(vcpu->kvm); + if (r) + return r; + write_lock(&vcpu->kvm->mmu_lock); r = make_mmu_pages_available(vcpu); if (r < 0) @@ -5481,9 +5485,13 @@ void kvm_mmu_init_vm(struct kvm *kvm) { struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker; - kvm_mmu_init_tdp_mmu(kvm); - - kvm->arch.memslots_have_rmaps = true; + if (!kvm_mmu_init_tdp_mmu(kvm)) + /* + * No smp_load/store wrappers needed here as we are in + * VM init and there cannot be any memslots / other threads + * accessing this struct kvm yet. + */ + kvm->arch.memslots_have_rmaps = true; node->track_write = kvm_mmu_pte_write; node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot; diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 95eeb5ac6a8a..ea00c9502ba1 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -14,10 +14,10 @@ static bool __read_mostly tdp_mmu_enabled = false; module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644); /* Initializes the TDP MMU for the VM, if enabled. */ -void kvm_mmu_init_tdp_mmu(struct kvm *kvm) +bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled)) - return; + return false; /* This should not be changed for the lifetime of the VM. */ kvm->arch.tdp_mmu_enabled = true; @@ -25,6 +25,8 @@ void kvm_mmu_init_tdp_mmu(struct kvm *kvm) INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots); spin_lock_init(&kvm->arch.tdp_mmu_pages_lock); INIT_LIST_HEAD(&kvm->arch.tdp_mmu_pages); + + return true; } static __always_inline void kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm, diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index 5fdf63090451..b046ab5137a1 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -80,12 +80,12 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level); #ifdef CONFIG_X86_64 -void kvm_mmu_init_tdp_mmu(struct kvm *kvm); +bool kvm_mmu_init_tdp_mmu(struct kvm *kvm); void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm); static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return kvm->arch.tdp_mmu_enabled; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; } #else -static inline void kvm_mmu_init_tdp_mmu(struct kvm *kvm) {} +static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7cbaa92687f7..28dc8bdd0c8a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10931,6 +10931,8 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot, int lpages = gfn_to_index(slot->base_gfn + npages - 1, slot->base_gfn, level) + 1; + WARN_ON(slot->arch.rmap[i]); + slot->arch.rmap[i] = kvcalloc(lpages, sz, GFP_KERNEL_ACCOUNT); if (!slot->arch.rmap[i]) { memslot_rmap_free(slot); @@ -10941,6 +10943,50 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot, return 0; } +int alloc_all_memslots_rmaps(struct kvm *kvm) +{ + struct kvm_memslots *slots; + struct kvm_memory_slot *slot; + int r, i; + + /* + * Check if memslots alreday have rmaps early before acquiring + * the slots_arch_lock below. + */ + if (kvm_memslots_have_rmaps(kvm)) + return 0; + + mutex_lock(&kvm->slots_arch_lock); + + /* + * Read memslots_have_rmaps again, under the slots arch lock, + * before allocating the rmaps + */ + if (kvm_memslots_have_rmaps(kvm)) { + mutex_unlock(&kvm->slots_arch_lock); + return 0; + } + + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { + slots = __kvm_memslots(kvm, i); + kvm_for_each_memslot(slot, slots) { + r = memslot_rmap_alloc(slot, slot->npages); + if (r) { + mutex_unlock(&kvm->slots_arch_lock); + return r; + } + } + } + + /* + * Ensure that memslots_have_rmaps becomes true strictly after + * all the rmap pointers are set. + */ + smp_store_release(&kvm->arch.memslots_have_rmaps, true); + mutex_unlock(&kvm->slots_arch_lock); + return 0; +} + static int kvm_alloc_memslot_metadata(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned long npages)