From patchwork Fri Oct 11 02:10:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13831955 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 B1CC31FA24B for ; Fri, 11 Oct 2024 02:11:17 +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=1728612680; cv=none; b=ot1fPeEJ9nB6MHrOjnxyor+Yw7sRQAe5PgIFMsaT5seySIwzVW8WZRYPMKyPAZV7Vylz6gDsDus3DoF5pmInTmfNo1wPU3CeHtWJj/JZx9jseaD3eK+UqP08WrOPxJ9L/08fnRkrnn9w/J2e7utQMxR9NZG3Dr+lg6P9BzEkiBg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728612680; c=relaxed/simple; bh=2l/4Exb4i+z5I5WlQFCs9q8cTS9KUprPX2RvYEEUZlk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Y26YOP+uMva9RXzofULxf1dloUY3y7tknlbz1T0n4PaRCxGstjc/AJBMQjW9aN92Zn0uPde4bDaM5wnthERJUMmc9saywTiORv6p3R97Wkd4OqTJ+rtN42RS0xZy4LrhZRgyniDqDygDuBgEE/EO+vHDSlRLJiIphPSwH/BUQ/I= 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=dNaVsba2; 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="dNaVsba2" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-7db8197d431so2259331a12.0 for ; Thu, 10 Oct 2024 19:11:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728612677; x=1729217477; 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=swbcLNUhlO+Z3x5j0iArPCyFfm9nB4ZdSOpt0u+BRiM=; b=dNaVsba2yMFVWf0wZyQTBbH4NTDwleWChlrKE53UQKNjNA5Yw6xXhT1oMavj92mvrK hROvdPEWLNajwQcFxBhu9Sid8+byTTn2eQVxMTDMn9bNP8rydbWAV7tIO2GCez3k2mUl M/1p/Vhiz6ghe2Yh9XXbFivonf7dp6qGqH7HNO7HheXhAMjkJKXODvf34AtRHx4yoD0m /huSs46IuuP3py8sBelqjaOy5olKInvBa85dMPmMwyUCQjDKV4/d0lV0MyyQq7WGUNze wJVKojKsQsRYWHdb82IJxLtFJ0rS0WqDHiWeEarRTIJ7A2EXUzsr2G7N+gttgmmsgOM1 mqYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728612677; x=1729217477; 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=swbcLNUhlO+Z3x5j0iArPCyFfm9nB4ZdSOpt0u+BRiM=; b=Xs4/tuFrpoLsafvszXToYG7GuR9WReXVBCLGmvD/dVyNHFtXKsJ/QrzC9Q+wswAYoB wQz9aFaCfjGewU0RvhhYWYzTUZrJgaYPJAkNVkItXIZMDc6lciVzybwtG3P48gGXK3Cl lyYJgoeWzLvK7+oYTDOmUhAQyBKZgTkXAIFBWXQI1O82Vg7YPx5oafQ0WRgpgMdYI3Z4 j2rlxJZofHW1WulQLqFoLNZ6dTo9emTlYlMB7aABe4VrlYwo3nSXUEWlQ7uYDCQMN/iF +fetSTTY5NNl5mT5VE+dndUo6pubcTOXt58rcg879ynC/T8CZq7whzWq6fc2Pcrqxsbm n7BQ== X-Gm-Message-State: AOJu0YxfBEv6wgyf0vB4tLdJ+IfKOZK8UazhT5+7CVSKnrWks0XOb/1W nGvT5yymVzhHld8Qw3ldTJvWOC5YfsSRGUcuCGLsNTgebh6+gEWdjNEAFrkg+I4iJwNb64iQ0Le b3w== X-Google-Smtp-Source: AGHT+IGBcUZAIBFhERfMhmqeQCLgWZgdChjmWr3g6PLndUtixM7vUgJQznL7pe9JB9jYv/yodxK5GriG5ZU= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:9d:3983:ac13:c240]) (user=seanjc job=sendgmr) by 2002:a17:902:d2c8:b0:20b:7ece:3225 with SMTP id d9443c01a7336-20ca130a1b1mr320995ad.0.1728612676949; Thu, 10 Oct 2024 19:11:16 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 10 Oct 2024 19:10:44 -0700 In-Reply-To: <20241011021051.1557902-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241011021051.1557902-1-seanjc@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241011021051.1557902-13-seanjc@google.com> Subject: [PATCH 12/18] KVM: x86/mmu: Use Accessed bit even when _hardware_ A/D bits are disabled From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yan Zhao , Sagi Shahar , " =?utf-8?q?Alex_Benn=C3=A9e?= " , David Matlack , James Houghton Use the Accessed bit in SPTEs even when A/D bits are disabled in hardware, i.e. propagate accessed information to SPTE.Accessed even when KVM is doing manual tracking by making SPTEs not-present. In addition to eliminating a small amount of code in is_accessed_spte(), this also paves the way for preserving Accessed information when a SPTE is zapped in response to a mmu_notifier PROTECTION event, e.g. if a SPTE is zapped because NUMA balancing kicks in. Note, EPT is the only flavor of paging in which A/D bits are conditionally enabled, and the Accessed (and Dirty) bit is software-available when A/D bits are disabled. Note #2, there are currently no concrete plans to preserve Accessed information. Explorations on that front were the initial catalyst, but the cleanup is the motivation for the actual commit. Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 3 ++- arch/x86/kvm/mmu/spte.c | 4 ++-- arch/x86/kvm/mmu/spte.h | 11 +---------- 3 files changed, 5 insertions(+), 13 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 06fb0fd3f87d..5be3b5f054f1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3486,7 +3486,8 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) * enabled, the SPTE can't be an access-tracked SPTE. */ if (unlikely(!kvm_ad_enabled) && is_access_track_spte(spte)) - new_spte = restore_acc_track_spte(new_spte); + new_spte = restore_acc_track_spte(new_spte) | + shadow_accessed_mask; /* * To keep things simple, only SPTEs that are MMU-writable can diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 54d8c9b76050..617479efd127 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -175,7 +175,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, spte |= shadow_present_mask; if (!prefetch || synchronizing) - spte |= spte_shadow_accessed_mask(spte); + spte |= shadow_accessed_mask; /* * For simplicity, enforce the NX huge page mitigation even if not @@ -346,7 +346,7 @@ u64 mark_spte_for_access_track(u64 spte) spte |= (spte & SHADOW_ACC_TRACK_SAVED_BITS_MASK) << SHADOW_ACC_TRACK_SAVED_BITS_SHIFT; - spte &= ~shadow_acc_track_mask; + spte &= ~(shadow_acc_track_mask | shadow_accessed_mask); return spte; } diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index 908cb672c4e1..c8dc75337c8b 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -316,12 +316,6 @@ static inline bool spte_ad_need_write_protect(u64 spte) return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_ENABLED; } -static inline u64 spte_shadow_accessed_mask(u64 spte) -{ - KVM_MMU_WARN_ON(!is_shadow_present_pte(spte)); - return spte_ad_enabled(spte) ? shadow_accessed_mask : 0; -} - static inline u64 spte_shadow_dirty_mask(u64 spte) { KVM_MMU_WARN_ON(!is_shadow_present_pte(spte)); @@ -355,10 +349,7 @@ static inline kvm_pfn_t spte_to_pfn(u64 pte) static inline bool is_accessed_spte(u64 spte) { - u64 accessed_mask = spte_shadow_accessed_mask(spte); - - return accessed_mask ? spte & accessed_mask - : !is_access_track_spte(spte); + return spte & shadow_accessed_mask; } static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte,