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Date:   Tue, 26 Apr 2022 05:39:02 +0000
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Subject: [PATCH v3 4/6] KVM: arm64/mmu: count KVM page table pages in
 pagetable stats
From:   Yosry Ahmed <yosryahmed@google.com>
To:     Sean Christopherson <seanjc@google.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Anup Patel <anup@brainfault.org>,
        Atish Patra <atishp@atishpatra.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        James Morse <james.morse@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
        Marc Zyngier <maz@kernel.org>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>
Cc:     linux-mips@vger.kernel.org, kvm@vger.kernel.org,
        kvm-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        kvmarm@lists.cs.columbia.edu, Yosry Ahmed <yosryahmed@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Count the pages used by KVM in arm64 for page tables in pagetable stats.

Account pages allocated for PTEs in pgtable init functions and
kvm_set_table_pte().

Since most page table pages are freed using put_page(), add a helper
function put_pte_page() that checks if this is the last ref for a pte
page before putting it, and unaccounts stats accordingly.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 arch/arm64/kernel/image-vars.h |  3 ++
 arch/arm64/kvm/hyp/pgtable.c   | 50 +++++++++++++++++++++-------------
 2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 241c86b67d01..25bf058714f6 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -143,6 +143,9 @@ KVM_NVHE_ALIAS(__hyp_rodata_end);
 /* pKVM static key */
 KVM_NVHE_ALIAS(kvm_protected_mode_initialized);
 
+/* Called by kvm_account_pgtable_pages() to update pagetable stats */
+KVM_NVHE_ALIAS(__mod_lruvec_page_state);
+
 #endif /* CONFIG_KVM */
 
 #endif /* __ARM64_KERNEL_IMAGE_VARS_H */
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 2cb3867eb7c2..53e13c3313e9 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -152,6 +152,7 @@ static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp,
 
 	WARN_ON(kvm_pte_valid(old));
 	smp_store_release(ptep, pte);
+	kvm_account_pgtable_pages((void *)childp, +1);
 }
 
 static kvm_pte_t kvm_init_valid_leaf_pte(u64 pa, kvm_pte_t attr, u32 level)
@@ -326,6 +327,14 @@ int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
 	return ret;
 }
 
+static void put_pte_page(kvm_pte_t *ptep, struct kvm_pgtable_mm_ops *mm_ops)
+{
+	/* If this is the last page ref, decrement pagetable stats first. */
+	if (!mm_ops->page_count || mm_ops->page_count(ptep) == 1)
+		kvm_account_pgtable_pages((void *)ptep, -1);
+	mm_ops->put_page(ptep);
+}
+
 struct hyp_map_data {
 	u64				phys;
 	kvm_pte_t			attr;
@@ -488,10 +497,10 @@ static int hyp_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 
 	dsb(ish);
 	isb();
-	mm_ops->put_page(ptep);
+	put_pte_page(ptep, mm_ops);
 
 	if (childp)
-		mm_ops->put_page(childp);
+		put_pte_page(childp, mm_ops);
 
 	return 0;
 }
@@ -522,6 +531,7 @@ int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits,
 	pgt->pgd = (kvm_pte_t *)mm_ops->zalloc_page(NULL);
 	if (!pgt->pgd)
 		return -ENOMEM;
+	kvm_account_pgtable_pages((void *)pgt->pgd, +1);
 
 	pgt->ia_bits		= va_bits;
 	pgt->start_level	= KVM_PGTABLE_MAX_LEVELS - levels;
@@ -541,10 +551,10 @@ static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	if (!kvm_pte_valid(pte))
 		return 0;
 
-	mm_ops->put_page(ptep);
+	put_pte_page(ptep, mm_ops);
 
 	if (kvm_pte_table(pte, level))
-		mm_ops->put_page(kvm_pte_follow(pte, mm_ops));
+		put_pte_page(kvm_pte_follow(pte, mm_ops), mm_ops);
 
 	return 0;
 }
@@ -558,7 +568,7 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
 	};
 
 	WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
-	pgt->mm_ops->put_page(pgt->pgd);
+	put_pte_page(pgt->pgd, pgt->mm_ops);
 	pgt->pgd = NULL;
 }
 
@@ -694,7 +704,7 @@ static void stage2_put_pte(kvm_pte_t *ptep, struct kvm_s2_mmu *mmu, u64 addr,
 		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, addr, level);
 	}
 
-	mm_ops->put_page(ptep);
+	put_pte_page(ptep, mm_ops);
 }
 
 static bool stage2_pte_cacheable(struct kvm_pgtable *pgt, kvm_pte_t pte)
@@ -795,7 +805,7 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 
 	if (data->anchor) {
 		if (stage2_pte_is_counted(pte))
-			mm_ops->put_page(ptep);
+			put_pte_page(ptep, mm_ops);
 
 		return 0;
 	}
@@ -848,8 +858,8 @@ static int stage2_map_walk_table_post(u64 addr, u64 end, u32 level,
 		childp = kvm_pte_follow(*ptep, mm_ops);
 	}
 
-	mm_ops->put_page(childp);
-	mm_ops->put_page(ptep);
+	put_pte_page(childp, mm_ops);
+	put_pte_page(ptep, mm_ops);
 
 	return ret;
 }
@@ -962,7 +972,7 @@ static int stage2_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	if (!kvm_pte_valid(pte)) {
 		if (stage2_pte_is_counted(pte)) {
 			kvm_clear_pte(ptep);
-			mm_ops->put_page(ptep);
+			put_pte_page(ptep, mm_ops);
 		}
 		return 0;
 	}
@@ -988,7 +998,7 @@ static int stage2_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 					       kvm_granule_size(level));
 
 	if (childp)
-		mm_ops->put_page(childp);
+		put_pte_page(childp, mm_ops);
 
 	return 0;
 }
@@ -1177,16 +1187,17 @@ int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
 			      enum kvm_pgtable_stage2_flags flags,
 			      kvm_pgtable_force_pte_cb_t force_pte_cb)
 {
-	size_t pgd_sz;
+	u32 pgd_num;
 	u64 vtcr = mmu->arch->vtcr;
 	u32 ia_bits = VTCR_EL2_IPA(vtcr);
 	u32 sl0 = FIELD_GET(VTCR_EL2_SL0_MASK, vtcr);
 	u32 start_level = VTCR_EL2_TGRAN_SL0_BASE - sl0;
 
-	pgd_sz = kvm_pgd_pages(ia_bits, start_level) * PAGE_SIZE;
-	pgt->pgd = mm_ops->zalloc_pages_exact(pgd_sz);
+	pgd_num = kvm_pgd_pages(ia_bits, start_level);
+	pgt->pgd = mm_ops->zalloc_pages_exact(pgd_num * PAGE_SIZE);
 	if (!pgt->pgd)
 		return -ENOMEM;
+	kvm_account_pgtable_pages((void *)pgt->pgd, +pgd_num);
 
 	pgt->ia_bits		= ia_bits;
 	pgt->start_level	= start_level;
@@ -1210,17 +1221,17 @@ static int stage2_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	if (!stage2_pte_is_counted(pte))
 		return 0;
 
-	mm_ops->put_page(ptep);
+	put_pte_page(ptep, mm_ops);
 
 	if (kvm_pte_table(pte, level))
-		mm_ops->put_page(kvm_pte_follow(pte, mm_ops));
+		put_pte_page(kvm_pte_follow(pte, mm_ops), mm_ops);
 
 	return 0;
 }
 
 void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
 {
-	size_t pgd_sz;
+	u32 pgd_num;
 	struct kvm_pgtable_walker walker = {
 		.cb	= stage2_free_walker,
 		.flags	= KVM_PGTABLE_WALK_LEAF |
@@ -1229,7 +1240,8 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
 	};
 
 	WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
-	pgd_sz = kvm_pgd_pages(pgt->ia_bits, pgt->start_level) * PAGE_SIZE;
-	pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz);
+	pgd_num = kvm_pgd_pages(pgt->ia_bits, pgt->start_level);
+	kvm_account_pgtable_pages((void *)pgt->pgd, -pgd_num);
+	pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_num * PAGE_SIZE);
 	pgt->pgd = NULL;
 }
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog