From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (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 DC6133806B0 for ; Fri, 5 Jun 2026 17:46:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780681581; cv=none; b=p6+6Jp8Na7QWFSZB8Zhver1+kIcYwcmhdeJp2EG0EJLM8qQJASjY+khFCcQOjWvehCE/Xp4GhYDHl2d+sKVDYIMgYPdZhHYNs7HJmSbxXuSNClnK+/iH4lAV2VX1pXWK8pn8+g+hT+iX7B+8whLzVAIuNJ2rMN1hUp3ydr4qgWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780681581; c=relaxed/simple; bh=MaGp98SPP5pLqA/SgDcjONweIRAww8zV/cITU0dzni4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=NPC5lVRxLhyw8R+X6uHiZbbgWu/TFqZTifsc0qbGm/lsa4+75ab+BnN28hGjlad7di04CGkpGR3TynF3xUkYIwutLYCmeRDMrmE8yJA7L1MCpJiJMUN0VPMcbTlsx4w95fWHJWrO6cJN9OLHYqxpO3uD9mNQsJx25IQWArRQkKU= 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=hLPmjcrO; arc=none smtp.client-ip=209.85.215.201 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="hLPmjcrO" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-c85a2cda4d0so1205313a12.3 for ; Fri, 05 Jun 2026 10:46:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780681576; x=1781286376; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=eJAya2rWHdwTV/i2f+Er10bBIZ9X+EeemiuR2u/Ktcg=; b=hLPmjcrOLQv8Fk/0+sIz7aqsAOcUWtQcMMs/gUMdknHrZFmtmVZ6LNSPN9kXZo/wNq 1G/ETn8Ck/4N8P2BNWh1QY+Z7MWlGJlxtUsFg3zS0tHtjZAU/G6wVws8nqsG1BUD6/PR fpLZGmVOYK3DRFOHie3R10z821mlxUZQvrP7SuQiKpgtNytDQNJb99tLgB5ha6BDrphE ezNbK8PdG9R5xu2xS2AMbpHc2bP4uecZkBMpsftqiB8QeG/hCkSJWwFNBzvQyn/bVG+9 HaUmfP+Fyjw4SXHwjBCcPwdoMx9FhnLsnVwJfGjbCtg/84e3xM0g917Nm2UkaXihU8P4 mP2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780681576; x=1781286376; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=eJAya2rWHdwTV/i2f+Er10bBIZ9X+EeemiuR2u/Ktcg=; b=hf1h1qUQFhto23KR6yLD4JnbT0pEblYWSzrtd5rMJDGB0sefWD/gVKbh6h/330KU6L gKJnmwkf1rI8W5udGx14eIQS0dGITti2Rly4gJZWd3iLVh5LdDYKf/rveIDIHIjpbr1N osvvFkB7+owq2FVrLzbm1aoXv0VQitIKDl5hP7YerETN1PQx59m7AuBap/5xmWIYcG7O 2pS0KvU0V8gOxnBK+oWpH37bxGvVURN3+ByMB3k/rNhZ2XQGIIclB//RNoYD/SiXd7ab UZls3uFCjEdOsekR0C8I9jOEw5M/64pXFdUw1A7jAfbWw1ThZCI94LiRYOOE+pi9iEvb PMbQ== X-Forwarded-Encrypted: i=1; AFNElJ9v9J73a5ZVNigaysf0jT/jsH0HfVz8mZ/jUQ97Mh8BQlpen15jgdzMpq96qV6OYxj7UI1ppjTbWNwuvQo=@vger.kernel.org X-Gm-Message-State: AOJu0YytZ6ZJ6c/q3TC/9hgy5ooKwi6pbfu8kVntn+tMaoRu/r4QZ/WN VPYBHxENpSxj+/rAzGjzgsGaeqMpGjkmCFWJNSQWbr9mDBxo4STr4r3cRtaFDabQJV3G6EgXKIf 4/Dj2Uw== X-Received: from pgam25.prod.google.com ([2002:a05:6a02:2b59:b0:c80:26d4:20ea]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:514:b0:3b4:b6d7:a992 with SMTP id adf61e73a8af0-3b4ccd1e2a2mr5750363637.8.1780681575824; Fri, 05 Jun 2026 10:46:15 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 5 Jun 2026 10:46:11 -0700 In-Reply-To: <20260605174611.2222504-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260605174611.2222504-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.1032.g2f8565e1d1-goog Message-ID: <20260605174611.2222504-3-seanjc@google.com> Subject: [PATCH 2/2] 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, Yosry Ahmed , Jim Mattson , James Houghton 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 --- arch/x86/include/asm/kvm_host.h | 1 + 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(+), 8 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3886b536c8a5..be84e4d2405e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1701,6 +1701,7 @@ 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 cd68a5bad0c6..e4cbecaa105d 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), -- 2.54.0.1032.g2f8565e1d1-goog