From patchwork Thu Aug 24 08:04:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Stevens X-Patchwork-Id: 13363698 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79231C71145 for ; Thu, 24 Aug 2023 08:07:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240464AbjHXIGj (ORCPT ); Thu, 24 Aug 2023 04:06:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240480AbjHXIGW (ORCPT ); Thu, 24 Aug 2023 04:06:22 -0400 Received: from mail-pf1-x432.google.com (mail-pf1-x432.google.com [IPv6:2607:f8b0:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F5931BDB for ; Thu, 24 Aug 2023 01:05:37 -0700 (PDT) Received: by mail-pf1-x432.google.com with SMTP id d2e1a72fcca58-68a41035828so3289684b3a.1 for ; Thu, 24 Aug 2023 01:05:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1692864314; x=1693469114; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=R3N2qLIV1dOCTfZGrxfezfZCNqk3aw3I6ITB122p148=; b=KmMnpYLR9IuJ5tdXymssdKkrVpHH6nCmiyCa3qQW4Rilr0JQFELA5m87ZWYfut3pmA fysrOxyV+ru/71qrasjIWXzkfsAP2+sXyOGC5ezD+7SC7LGvnaruJNY8kw15hsYmQHfX 8IQzokZvhpXo049qUnE0rm8sLA2ng20KMTZBM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692864314; x=1693469114; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=R3N2qLIV1dOCTfZGrxfezfZCNqk3aw3I6ITB122p148=; b=gyrMx+0Q8Ibshehwbgh7fQRrh+7AYcHkhm90KoXj3ApNqpT9WfdFnw1OIXoRnlQZlG 3usw9/1qBVTgRqnKykDdVvuJkpSSrnaDPK0/nU9qk8E6sw3XWmjn+KaGpyqwUTY8MR7/ 8l1P7zXxSQc7i3c8yOEXB1caEwOd53E4gFvGTZS9lcyL4jXcXk1GYdr5bmca/HERz2gD d/pW+yPBtZdPEgvafyQpbz5sw1acA0E9wMYpg1W0oUQv2bosWwU4U5sHWM4rtTXDCpGs g/O45kVhCNbygmsIF1wu0UrpJCLoxVgFpFntfhiknsUlwA1efgHGw+ab+jppniKhRRfl tvVQ== X-Gm-Message-State: AOJu0Yzxj0K0Z3trYe60SMT2mXy9iWnglmRUdoj5C6naVgMcM18oNlHB psAxdwDgx+BYKhqwOikjQSMFsQ== X-Google-Smtp-Source: AGHT+IFQuzhiw+VNrMdIrBf0Ryoivf1q43SH2TuxYQh6Y66LpJ63BZQmwO6ZvOpnuBz8ux1MkDgcBA== X-Received: by 2002:a05:6a21:778a:b0:14b:83f7:ef4f with SMTP id bd10-20020a056a21778a00b0014b83f7ef4fmr3998192pzc.34.1692864313823; Thu, 24 Aug 2023 01:05:13 -0700 (PDT) Received: from localhost ([2401:fa00:8f:203:515:8b2a:90c3:b79e]) by smtp.gmail.com with UTF8SMTPSA id m14-20020aa7900e000000b0068a3f861b24sm7002699pfo.195.2023.08.24.01.05.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Aug 2023 01:05:13 -0700 (PDT) From: David Stevens X-Google-Original-From: David Stevens To: Sean Christopherson Cc: Yu Zhang , Isaku Yamahata , Marc Zyngier , Michael Ellerman , Peter Xu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, David Stevens Subject: [PATCH v8 5/8] KVM: x86/mmu: Don't pass FOLL_GET to __kvm_follow_pfn Date: Thu, 24 Aug 2023 17:04:05 +0900 Message-ID: <20230824080408.2933205-6-stevensd@google.com> X-Mailer: git-send-email 2.42.0.rc1.204.g551eb34607-goog In-Reply-To: <20230824080408.2933205-1-stevensd@google.com> References: <20230824080408.2933205-1-stevensd@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Stevens Stop passing FOLL_GET to __kvm_follow_pfn. This allows the host to map memory into the guest that is backed by un-refcounted struct pages - for example, the tail pages of higher order non-compound pages allocated by the amdgpu driver via ttm_pool_alloc_page. The bulk of this change is tracking the is_refcounted_page flag so that non-refcounted pages don't trigger page_count() == 0 warnings. This is done by storing the flag in an unused bit in the sptes. This only bit is not available in PAE SPTEs, so FOLL_GET is only omitted for TDP on x86-64. Signed-off-by: David Stevens --- arch/x86/kvm/mmu/mmu.c | 55 +++++++++++++++++++++++---------- arch/x86/kvm/mmu/mmu_internal.h | 1 + arch/x86/kvm/mmu/paging_tmpl.h | 8 +++-- arch/x86/kvm/mmu/spte.c | 4 ++- arch/x86/kvm/mmu/spte.h | 12 ++++++- arch/x86/kvm/mmu/tdp_mmu.c | 22 +++++++------ include/linux/kvm_host.h | 3 ++ virt/kvm/kvm_main.c | 6 ++-- 8 files changed, 79 insertions(+), 32 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index dabae67f198b..4f5d33e95c6e 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -553,12 +553,14 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) { flush = true; - kvm_set_pfn_accessed(spte_to_pfn(old_spte)); + if (is_refcounted_page_pte(old_spte)) + kvm_set_page_accessed(pfn_to_page(spte_to_pfn(old_spte))); } if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) { flush = true; - kvm_set_pfn_dirty(spte_to_pfn(old_spte)); + if (is_refcounted_page_pte(old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(old_spte))); } return flush; @@ -596,14 +598,18 @@ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep) * before they are reclaimed. Sanity check that, if the pfn is backed * by a refcounted page, the refcount is elevated. */ - page = kvm_pfn_to_refcounted_page(pfn); - WARN_ON(page && !page_count(page)); + if (is_refcounted_page_pte(old_spte)) { + page = kvm_pfn_to_refcounted_page(pfn); + WARN_ON(!page || !page_count(page)); + } - if (is_accessed_spte(old_spte)) - kvm_set_pfn_accessed(pfn); + if (is_refcounted_page_pte(old_spte)) { + if (is_accessed_spte(old_spte)) + kvm_set_page_accessed(pfn_to_page(pfn)); - if (is_dirty_spte(old_spte)) - kvm_set_pfn_dirty(pfn); + if (is_dirty_spte(old_spte)) + kvm_set_page_dirty(pfn_to_page(pfn)); + } return old_spte; } @@ -639,8 +645,8 @@ static bool mmu_spte_age(u64 *sptep) * Capture the dirty status of the page, so that it doesn't get * lost when the SPTE is marked for access tracking. */ - if (is_writable_pte(spte)) - kvm_set_pfn_dirty(spte_to_pfn(spte)); + if (is_writable_pte(spte) && is_refcounted_page_pte(spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(spte))); spte = mark_spte_for_access_track(spte); mmu_spte_update_no_track(sptep, spte); @@ -1278,8 +1284,8 @@ static bool spte_wrprot_for_clear_dirty(u64 *sptep) { bool was_writable = test_and_clear_bit(PT_WRITABLE_SHIFT, (unsigned long *)sptep); - if (was_writable && !spte_ad_enabled(*sptep)) - kvm_set_pfn_dirty(spte_to_pfn(*sptep)); + if (was_writable && !spte_ad_enabled(*sptep) && is_refcounted_page_pte(*sptep)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(*sptep))); return was_writable; } @@ -2937,6 +2943,11 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, bool host_writable = !fault || fault->map_writable; bool prefetch = !fault || fault->prefetch; bool write_fault = fault && fault->write; + /* + * Prefetching uses gfn_to_page_many_atomic, which never gets + * non-refcounted pages. + */ + bool is_refcounted = !fault || fault->is_refcounted_page; pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__, *sptep, write_fault, gfn); @@ -2969,7 +2980,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, } wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch, - true, host_writable, &spte); + true, host_writable, is_refcounted, &spte); if (*sptep == spte) { ret = RET_PF_SPURIOUS; @@ -4296,11 +4307,19 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot; + /* + * We only allow non-refcounted pages if we can track whether or not + * pages are refcounted via an SPTE bit. This bit is not available + * in PAE SPTEs, so pass FOLL_GET if we may have to deal with those. + */ + unsigned int get_flag = (tdp_enabled && IS_ENABLED(CONFIG_X86_64)) ? + 0 : FOLL_GET; struct kvm_follow_pfn foll = { .slot = slot, .gfn = fault->gfn, - .flags = FOLL_GET | (fault->write ? FOLL_WRITE : 0), + .flags = (fault->write ? FOLL_WRITE : 0) | get_flag, .try_map_writable = true, + .guarded_by_mmu_notifier = true, }; /* @@ -4317,6 +4336,7 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault fault->slot = NULL; fault->pfn = KVM_PFN_NOSLOT; fault->map_writable = false; + fault->is_refcounted_page = false; return RET_PF_CONTINUE; } /* @@ -4372,6 +4392,7 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault success: fault->hva = foll.hva; fault->map_writable = foll.writable; + fault->is_refcounted_page = foll.is_refcounted_page; return RET_PF_CONTINUE; } @@ -4456,8 +4477,9 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault r = direct_map(vcpu, fault); out_unlock: + if (fault->is_refcounted_page) + kvm_set_page_accessed(pfn_to_page(fault->pfn)); write_unlock(&vcpu->kvm->mmu_lock); - kvm_release_pfn_clean(fault->pfn); return r; } @@ -4534,8 +4556,9 @@ static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu, r = kvm_tdp_mmu_map(vcpu, fault); out_unlock: + if (fault->is_refcounted_page) + kvm_set_page_accessed(pfn_to_page(fault->pfn)); read_unlock(&vcpu->kvm->mmu_lock); - kvm_release_pfn_clean(fault->pfn); return r; } #endif diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index d39af5639ce9..55790085884f 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -240,6 +240,7 @@ struct kvm_page_fault { kvm_pfn_t pfn; hva_t hva; bool map_writable; + bool is_refcounted_page; /* * Indicates the guest is trying to write a gfn that contains one or diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 0662e0278e70..4ffcebc0c3ce 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -828,8 +828,9 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault r = FNAME(fetch)(vcpu, fault, &walker); out_unlock: + if (fault->is_refcounted_page) + kvm_set_page_accessed(pfn_to_page(fault->pfn)); write_unlock(&vcpu->kvm->mmu_lock); - kvm_release_pfn_clean(fault->pfn); return r; } @@ -883,7 +884,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, */ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i) { - bool host_writable; + bool host_writable, is_refcounted; gpa_t first_pte_gpa; u64 *sptep, spte; struct kvm_memory_slot *slot; @@ -940,10 +941,11 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int sptep = &sp->spt[i]; spte = *sptep; host_writable = spte & shadow_host_writable_mask; + is_refcounted = spte & SPTE_MMU_PAGE_REFCOUNTED; slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); make_spte(vcpu, sp, slot, pte_access, gfn, spte_to_pfn(spte), spte, true, false, - host_writable, &spte); + host_writable, is_refcounted, &spte); return mmu_spte_update(sptep, spte); } diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index cf2c6426a6fc..5b13d9143d56 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -138,7 +138,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, const struct kvm_memory_slot *slot, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch, bool can_unsync, - bool host_writable, u64 *new_spte) + bool host_writable, bool is_refcounted, u64 *new_spte) { int level = sp->role.level; u64 spte = SPTE_MMU_PRESENT_MASK; @@ -188,6 +188,8 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (level > PG_LEVEL_4K) spte |= PT_PAGE_SIZE_MASK; + if (is_refcounted) + spte |= SPTE_MMU_PAGE_REFCOUNTED; if (shadow_memtype_mask) spte |= static_call(kvm_x86_get_mt_mask)(vcpu, gfn, diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index 1279db2eab44..be93dd061ae3 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -95,6 +95,11 @@ static_assert(!(EPT_SPTE_MMU_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK)); /* Defined only to keep the above static asserts readable. */ #undef SHADOW_ACC_TRACK_SAVED_MASK +/* + * Indicates that the SPTE refers to a page with a valid refcount. + */ +#define SPTE_MMU_PAGE_REFCOUNTED BIT_ULL(59) + /* * Due to limited space in PTEs, the MMIO generation is a 19 bit subset of * the memslots generation and is derived as follows: @@ -332,6 +337,11 @@ static inline bool is_dirty_spte(u64 spte) return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK; } +static inline bool is_refcounted_page_pte(u64 spte) +{ + return spte & SPTE_MMU_PAGE_REFCOUNTED; +} + static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte, int level) { @@ -462,7 +472,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, const struct kvm_memory_slot *slot, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch, bool can_unsync, - bool host_writable, u64 *new_spte); + bool host_writable, bool is_refcounted, u64 *new_spte); u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, union kvm_mmu_page_role role, int index); u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 512163d52194..a9b1b14d2e26 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -474,6 +474,7 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, bool was_leaf = was_present && is_last_spte(old_spte, level); bool is_leaf = is_present && is_last_spte(new_spte, level); bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte); + bool is_refcounted = is_refcounted_page_pte(old_spte); WARN_ON(level > PT64_ROOT_MAX_LEVEL); WARN_ON(level < PG_LEVEL_4K); @@ -538,9 +539,9 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, if (is_leaf != was_leaf) kvm_update_page_stats(kvm, level, is_leaf ? 1 : -1); - if (was_leaf && is_dirty_spte(old_spte) && + if (was_leaf && is_dirty_spte(old_spte) && is_refcounted && (!is_present || !is_dirty_spte(new_spte) || pfn_changed)) - kvm_set_pfn_dirty(spte_to_pfn(old_spte)); + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(old_spte))); /* * Recursively handle child PTs if the change removed a subtree from @@ -552,9 +553,9 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed))) handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared); - if (was_leaf && is_accessed_spte(old_spte) && + if (was_leaf && is_accessed_spte(old_spte) && is_refcounted && (!is_present || !is_accessed_spte(new_spte) || pfn_changed)) - kvm_set_pfn_accessed(spte_to_pfn(old_spte)); + kvm_set_page_accessed(pfn_to_page(spte_to_pfn(old_spte))); } /* @@ -988,8 +989,9 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL); else wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn, - fault->pfn, iter->old_spte, fault->prefetch, true, - fault->map_writable, &new_spte); + fault->pfn, iter->old_spte, fault->prefetch, true, + fault->map_writable, fault->is_refcounted_page, + &new_spte); if (new_spte == iter->old_spte) ret = RET_PF_SPURIOUS; @@ -1205,8 +1207,9 @@ static bool age_gfn_range(struct kvm *kvm, struct tdp_iter *iter, * Capture the dirty status of the page, so that it doesn't get * lost when the SPTE is marked for access tracking. */ - if (is_writable_pte(iter->old_spte)) - kvm_set_pfn_dirty(spte_to_pfn(iter->old_spte)); + if (is_writable_pte(iter->old_spte) && + is_refcounted_page_pte(iter->old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(iter->old_spte))); new_spte = mark_spte_for_access_track(iter->old_spte); iter->old_spte = kvm_tdp_mmu_write_spte(iter->sptep, @@ -1626,7 +1629,8 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root, trace_kvm_tdp_mmu_spte_changed(iter.as_id, iter.gfn, iter.level, iter.old_spte, iter.old_spte & ~dbit); - kvm_set_pfn_dirty(spte_to_pfn(iter.old_spte)); + if (is_refcounted_page_pte(iter.old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(iter.old_spte))); } rcu_read_unlock(); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 713fc2d91f95..292701339198 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1157,6 +1157,9 @@ unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot, gfn_t gfn, void kvm_release_page_clean(struct page *page); void kvm_release_page_dirty(struct page *page); +void kvm_set_page_accessed(struct page *page); +void kvm_set_page_dirty(struct page *page); + struct kvm_follow_pfn { const struct kvm_memory_slot *slot; gfn_t gfn; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 963b96cd8ff9..fa1848c6c84f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2949,17 +2949,19 @@ static bool kvm_is_ad_tracked_page(struct page *page) return !PageReserved(page); } -static void kvm_set_page_dirty(struct page *page) +void kvm_set_page_dirty(struct page *page) { if (kvm_is_ad_tracked_page(page)) SetPageDirty(page); } +EXPORT_SYMBOL_GPL(kvm_set_page_dirty); -static void kvm_set_page_accessed(struct page *page) +void kvm_set_page_accessed(struct page *page) { if (kvm_is_ad_tracked_page(page)) mark_page_accessed(page); } +EXPORT_SYMBOL_GPL(kvm_set_page_accessed); void kvm_release_page_clean(struct page *page) {