From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 E7393392C2E for ; Fri, 12 Jun 2026 13:37:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781271451; cv=none; b=NmUfuU5icK5tjDtuiHMylFHla4K570qEaHgVI2zHc1eeI6xevWJbxSROkGLZeyUCdWYad7u8d77bzqItELJWgMB1i4K3Zp+0KzHBZ/Ev8Z5y5Y5y5XScnOpAxGTSITVNLZQkQ2CNLE1f3sAfsbHobd5KAzWpnrSeD5RGaoC23zs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781271451; c=relaxed/simple; bh=TJ50PwBAfuABED22863kivK320tuLglF5DIXcDN8CR4=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=EJAX6PMzHRfBaDEBAq+XCRGtpeKkdK7wkQPZzrLJOx11Kj8WP2PrnA2QB0UjlAuGff9bZIvd6pr4aiUlYTIFen79euWlHCcXRBgYAgjqMqZaTpA2ni+k+k3TS8OfV8igip/0o5ii4AQDG0TXBIx6OfyHaiz0evr0MgVxp2dZz00= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=GOj5eLMs; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="GOj5eLMs" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-36d98b5a68fso1770346a91.2 for ; Fri, 12 Jun 2026 06:37:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1781271449; x=1781876249; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=IPOJWxYYWDWDnJINU6K8lAt52NscNTk4Ebm3y3at6hM=; b=GOj5eLMsjgduBepur+ueOVeu8WKCup6npR0mf5VyIh4CVedcFHPop8gQw6lzg+Zjb3 lmQrVUfSxJxNHGlKIr1gGcf+vEepc4nZhIXKJybDRQ7RmlO2upRQIl/YtBADIzH65lyy 69qWVtagcW/IpoSjuS7XY2ABTuJsEvBph5ApMlYJYcXoTNERYT7Mk3rWZCsvnwmUqt0+ xKrFQTA2MfiIjetquLzyKqR/Dv17o2WfKHKY/Mf6If+mWzMCnZMTbSyW4e+QP/eNuQzw TlPDfXfp/vqh1eNpOg9kLGT4p+7OR9zBLrFR8s7xEqV04aURgpV5h9P22xHlxTLDWbWV tGbQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781271449; x=1781876249; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=IPOJWxYYWDWDnJINU6K8lAt52NscNTk4Ebm3y3at6hM=; b=q021R/5S0An9E1C52Z2P0QoE6w66ws0SH4BbNUjC7rWB8aqpFgbA6QPgzCfXqFHnxu ukjyBKZDzR45Slmiiuat51chd8sQQhrkY+u4gjiIHa38xhTyBoqBOAbcJAqb17uad3rL l+AYT3beoYPJQ208XalfthL/eoXv8l19+nc7n0mIslhlo+DuYwH/Lcl1+81M4LHJFJ55 jph/txCkbESv4aodLDOWqoAy8wZvwalZirMD46IjWqi3/ZR1ED6dOrskb0TyOBcc7LCM TnFthgmdPbZ8ncDMVk6Lg9GO6AmTD29rNQ7etDRWV5M7ri2/wU9CiYU0X8iShzjaiv4I SkNA== X-Forwarded-Encrypted: i=1; AFNElJ9WPaJZcnh+HXFnXqGRoOJ0vlR1brGH3qGaljJP0Oj5Dy4GWVheBTN20h1WHu1Ny6+hGSfE9VKCFW4uTGs=@vger.kernel.org X-Gm-Message-State: AOJu0YxKMWfthfTSoYVCWrDebJ2wSMex7YzvcaaBJo43uI0ULtZgifG6 6W1yK3i6hydFb6Uf7DpP/kOiDk7uy6vstbIH7f6evR5XUA1XIuRft73tK41x2LzocFGfjuOu16o N0ckCEw== X-Received: from pjff14.prod.google.com ([2002:a17:90b:562e:b0:369:2b54:e186]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:28c4:b0:35f:b987:4dac with SMTP id 98e67ed59e1d1-37a038e1f1fmr3171494a91.12.1781271449147; Fri, 12 Jun 2026 06:37:29 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 12 Jun 2026 06:37:27 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.54.0.1136.gdb2ca164c4-goog Message-ID: <20260612133727.411902-1-seanjc@google.com> Subject: [PATCH v2] KVM: x86/mmu: Expose number of shadow MMU shadow pages as a stat From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Turn arch.n_used_mmu_pages into a stat, mmu_shadow_pages, as the number of live shadow pages is arguably _the_ most critical datapoint when it comes to analyzing the shadow MMU. Before the TDP MMU came along, i.e. when the shadow MMU was the only MMU, explicitly tracking the number of shadow pages wasn't as interesting, because the same information could more or less be gleaned from the pages_{1g,2m,4k} stats. But with the TDP MMU, where the shadow MMU is only used for nested TDP, it becomes extremely difficult, if not impossible, to determine which SPTEs are coming from the TDP MMU, and which are coming from the shadow MMU. E.g. when triaging/debugging shadow MMU performance issues due to "too many shadow pages", being able to observe that 99%+ of all shadow pages are unsync is critical to being able to deduce that KVM is effectively leaking shadow pages. Signed-off-by: Sean Christopherson --- v2: Drop the definition of n_used_mmu_pages. [Sashiko] v1: https://lore.kernel.org/all/20260605174611.2222504-3-seanjc@google.com arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/mmu/mmu.c | 14 +++++++------- arch/x86/kvm/mmu/mmutrace.h | 2 +- arch/x86/kvm/x86.c | 1 + 4 files changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3886b536c8a5..c2b86b1420d1 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1435,7 +1435,6 @@ enum kvm_mmu_type { }; struct kvm_arch { - unsigned long n_used_mmu_pages; unsigned long n_requested_mmu_pages; unsigned long n_max_mmu_pages; unsigned int indirect_shadow_pages; @@ -1701,6 +1700,7 @@ struct kvm_vm_stat { u64 mmu_recycled; u64 mmu_cache_miss; u64 mmu_unsync; + u64 mmu_shadow_pages; union { struct { atomic64_t pages_4k; diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 9368a71336fe..3839aef6819b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1801,13 +1801,13 @@ static void kvm_mmu_check_sptes_at_free(struct kvm_mmu_page *sp) static void kvm_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) { - kvm->arch.n_used_mmu_pages++; + kvm->stat.mmu_shadow_pages++; kvm_account_pgtable_pages((void *)sp->spt, +1); } static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) { - kvm->arch.n_used_mmu_pages--; + kvm->stat.mmu_shadow_pages--; kvm_account_pgtable_pages((void *)sp->spt, -1); } @@ -2833,9 +2833,9 @@ static unsigned long kvm_mmu_zap_oldest_mmu_pages(struct kvm *kvm, static inline unsigned long kvm_mmu_available_pages(struct kvm *kvm) { - if (kvm->arch.n_max_mmu_pages > kvm->arch.n_used_mmu_pages) + if (kvm->arch.n_max_mmu_pages > kvm->stat.mmu_shadow_pages) return kvm->arch.n_max_mmu_pages - - kvm->arch.n_used_mmu_pages; + kvm->stat.mmu_shadow_pages; return 0; } @@ -2871,11 +2871,11 @@ void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned long goal_nr_mmu_pages) { write_lock(&kvm->mmu_lock); - if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) { - kvm_mmu_zap_oldest_mmu_pages(kvm, kvm->arch.n_used_mmu_pages - + if (kvm->stat.mmu_shadow_pages > goal_nr_mmu_pages) { + kvm_mmu_zap_oldest_mmu_pages(kvm, kvm->stat.mmu_shadow_pages - goal_nr_mmu_pages); - goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages; + goal_nr_mmu_pages = kvm->stat.mmu_shadow_pages; } kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages; diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h index fa01719baf8d..8354d9f39777 100644 --- a/arch/x86/kvm/mmu/mmutrace.h +++ b/arch/x86/kvm/mmu/mmutrace.h @@ -303,7 +303,7 @@ TRACE_EVENT( TP_fast_assign( __entry->mmu_valid_gen = kvm->arch.mmu_valid_gen; - __entry->mmu_used_pages = kvm->arch.n_used_mmu_pages; + __entry->mmu_used_pages = kvm->stat.mmu_shadow_pages; ), TP_printk("kvm-mmu-valid-gen %u used_pages %x", diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index cf122b8c3210..9d43e476707e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -244,6 +244,7 @@ const struct kvm_stats_desc kvm_vm_stats_desc[] = { STATS_DESC_COUNTER(VM, mmu_recycled), STATS_DESC_COUNTER(VM, mmu_cache_miss), STATS_DESC_ICOUNTER(VM, mmu_unsync), + STATS_DESC_ICOUNTER(VM, mmu_shadow_pages), STATS_DESC_ICOUNTER(VM, pages_4k), STATS_DESC_ICOUNTER(VM, pages_2m), STATS_DESC_ICOUNTER(VM, pages_1g), base-commit: de3a35be92d2391ece4bf3143ef2887192625fd0 -- 2.54.0.1136.gdb2ca164c4-goog