From patchwork Wed Feb 21 07:25:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Stevens X-Patchwork-Id: 13565028 Received: from mail-pf1-f172.google.com (mail-pf1-f172.google.com [209.85.210.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C79823E474 for ; Wed, 21 Feb 2024 07:26:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708500395; cv=none; b=VExc+PxnCyS1ic9VAWMVUNdUMKFLkmsEBsdFdhAPinA3An8P4xlG8kZP2QFZnl+A7+y7zNIzfCeDGc6GHRdXZ+UMvGhvTltZHX2azZZp4NSsSf06wWhy6fGnrM1gCkPXcRvaRZ90XXgcaRhKm+ovvG9Vx3xp9jaegG1pCxRh5rs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708500395; c=relaxed/simple; bh=AYMUk1nvkZ0pOB+n2DH+4BB79ShWznzgSUYd6B9JA90=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VVYcLpY9ytQOM3go8kz04Bc7WFKufeIaajtLrxzfTXQAAT1j3NFUYm02nMG8SKaAsar93Bw2YlTkMtoTwdlyRN+r1gtDV+rbMNuIXzitdBEfXVZdjkqUaEfILSUCZ6mBNID9mo2zWa3z3TMeXByXjRECej/JPrDF8qwFKrMHgG8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=E7R7pY0u; arc=none smtp.client-ip=209.85.210.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="E7R7pY0u" Received: by mail-pf1-f172.google.com with SMTP id d2e1a72fcca58-6e32a92e0fdso1392338b3a.0 for ; Tue, 20 Feb 2024 23:26:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1708500393; x=1709105193; darn=vger.kernel.org; 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=xgeyG0UvxcnYtwi28aLl5IuMoT6toXx2G8RTHGphwOY=; b=E7R7pY0u5nrNKFuxlnOiEpSpxbIOF79gNUag1hzPcC7uedzG1UOhuA9Fk0UypaGKNh rl3hqH5AxeH7EcVuivA2OkaBCRGP8Q+rl+XZ2w4KUa7Hx0xShV1Goe78WF0AeAzFl0Vj VCu91Q59HWGltxhui2e4wQN7Bxw6EKgv8PHPs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708500393; x=1709105193; 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=xgeyG0UvxcnYtwi28aLl5IuMoT6toXx2G8RTHGphwOY=; b=BzOzAvmIOCNVZH8qrDhfvTlZTJX46rcy1eFV+YSwZ1EhjleGw+V07c61F3nJxPk+PP dc3+HPimSzZ53iPSc1WK78gl+adHJwOYLjwEMOFotjbAbJdbI761nXkP2ItXPZyqfRa4 vZar/5PnH+0KVfbsfsIDV96FKVWuiYdEKfrHKk/9EOKFXhN5zEEVAqg+i5PxepwfK/9e 38nvpk/YqapYMwnaPygZay4NQ1cmVi1FwhGDg8hrRZoUWiPVRs22MUhl9FY5fWMPARlv 9egRMx8up7F3H8X2bnLFbUbYxOoj9EwVCr/ezmyMbord9PUvRC0HJGObKrS+48t9ckua yizg== X-Forwarded-Encrypted: i=1; AJvYcCUV5FLfQjAe0hceZcqOrkOGqIja6U/a5y6BRZ31n/hDazypwnOy/m0DUxqXzMaAZ8/TXEnSP76Fp5s7gIS9M55iTGEu X-Gm-Message-State: AOJu0YwCWoKKnKqCABsb64g5WC6t3JqoDi0Dpio+729RnkrtVHfQRFSx RuHK3rwYbLwMJhsezxoKZ1d3iSXLdEuCaOCfV8VAKF7BDncw1/MXWlVYO3rUNg== X-Google-Smtp-Source: AGHT+IGuCxXShC3TFTeo1X9CXGBptbturF8sPZMd5jwJbvXk6SCalhFEJjwEJN/EjoqrumaAkEOtBA== X-Received: by 2002:a05:6a00:1c8a:b0:6e4:69ac:4c94 with SMTP id y10-20020a056a001c8a00b006e469ac4c94mr7174801pfw.34.1708500393070; Tue, 20 Feb 2024 23:26:33 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:b417:5d09:c226:a19c]) by smtp.gmail.com with UTF8SMTPSA id v13-20020a62a50d000000b006e45a0feffasm6019256pfm.71.2024.02.20.23.26.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Feb 2024 23:26:32 -0800 (PST) From: David Stevens X-Google-Original-From: David Stevens To: Sean Christopherson Cc: Yu Zhang , Isaku Yamahata , Zhi Wang , Maxim Levitsky , kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, David Stevens Subject: [PATCH v10 7/8] KVM: x86/mmu: Track if sptes refer to refcounted pages Date: Wed, 21 Feb 2024 16:25:27 +0900 Message-ID: <20240221072528.2702048-10-stevensd@google.com> X-Mailer: git-send-email 2.44.0.rc0.258.g7320e95886-goog In-Reply-To: <20240221072528.2702048-1-stevensd@google.com> References: <20240221072528.2702048-1-stevensd@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: David Stevens Use one of the unused bits in EPT sptes to track whether or not an spte refers to a struct page that has a valid refcount, in preparation for adding support for mapping such pages into guests. The new bit is used to avoid triggering a page_count() == 0 warning and to avoid touching A/D bits of unknown usage. Non-EPT sptes don't have any free bits to use, so this tracking is not possible when TDP is disabled or on 32-bit x86. Signed-off-by: David Stevens --- arch/x86/kvm/mmu/mmu.c | 43 +++++++++++++++++++--------------- arch/x86/kvm/mmu/paging_tmpl.h | 5 ++-- arch/x86/kvm/mmu/spte.c | 4 +++- arch/x86/kvm/mmu/spte.h | 22 ++++++++++++++++- arch/x86/kvm/mmu/tdp_mmu.c | 21 ++++++++++------- include/linux/kvm_host.h | 3 +++ virt/kvm/kvm_main.c | 6 +++-- 7 files changed, 70 insertions(+), 34 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index bbeb0f6783d7..7c059b23ae16 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -541,12 +541,14 @@ 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_spte(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_spte(old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(old_spte))); } return flush; @@ -578,20 +580,23 @@ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep) pfn = spte_to_pfn(old_spte); - /* - * KVM doesn't hold a reference to any pages mapped into the guest, and - * instead uses the mmu_notifier to ensure that KVM unmaps any pages - * 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_ONCE(page && !page_count(page)); + if (is_refcounted_page_spte(old_spte)) { + /* + * KVM doesn't hold a reference to any pages mapped into the + * guest, and instead uses the mmu_notifier to ensure that KVM + * unmaps any pages 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_ONCE(!page || !page_count(page)); - if (is_accessed_spte(old_spte)) - kvm_set_pfn_accessed(pfn); + 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; } @@ -627,8 +632,8 @@ 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_spte(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); @@ -1267,8 +1272,8 @@ 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_spte(*sptep)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(*sptep))); return was_writable; } @@ -2946,7 +2951,7 @@ 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, true, &spte); if (*sptep == spte) { ret = RET_PF_SPURIOUS; diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 4d4e98fe4f35..c965f77ac4d5 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -902,7 +902,7 @@ 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; @@ -959,10 +959,11 @@ 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 = is_refcounted_page_spte(spte); 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 4a599130e9c9..efba85df6518 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 (spte_has_refcount_bit() && 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 a129951c9a88..4101cc9ef52f 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -96,6 +96,11 @@ 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: @@ -345,6 +350,21 @@ static inline bool is_dirty_spte(u64 spte) return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK; } +/* + * Extra bits are only available for TDP SPTEs, since bits 62:52 are reserved + * for PAE paging, including NPT PAE. When a tracking bit isn't available, we + * will reject mapping non-refcounted struct pages. + */ +static inline bool spte_has_refcount_bit(void) +{ + return tdp_enabled && IS_ENABLED(CONFIG_X86_64); +} + +static inline bool is_refcounted_page_spte(u64 spte) +{ + return !spte_has_refcount_bit() || (spte & SPTE_MMU_PAGE_REFCOUNTED); +} + static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte, int level) { @@ -475,7 +495,7 @@ 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 6ae19b4ee5b1..ee497fb78d90 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -414,6 +414,7 @@ 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_spte(old_spte); WARN_ON_ONCE(level > PT64_ROOT_MAX_LEVEL); WARN_ON_ONCE(level < PG_LEVEL_4K); @@ -478,9 +479,9 @@ 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 @@ -492,9 +493,9 @@ 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))); } /* @@ -956,8 +957,8 @@ 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, true, &new_spte); if (new_spte == iter->old_spte) ret = RET_PF_SPURIOUS; @@ -1178,8 +1179,9 @@ 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_spte(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, @@ -1602,7 +1604,8 @@ 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_spte(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 f72c79f159a2..cff5df6b0c52 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1211,6 +1211,9 @@ 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 5d66d841e775..e53a14adf149 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3281,17 +3281,19 @@ 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) {