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From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Vipin Sharma <vipinsh@google.com>,
	David Matlack <dmatlack@google.com>,
	Ben Gardon <bgardon@google.com>
Subject: [PATCH v4 02/13] KVM: x86/mmu: Use kvm_ad_enabled() to determine if TDP MMU SPTEs need wrprot
Date: Tue, 21 Mar 2023 15:00:10 -0700	[thread overview]
Message-ID: <20230321220021.2119033-3-seanjc@google.com> (raw)
In-Reply-To: <20230321220021.2119033-1-seanjc@google.com>

From: Vipin Sharma <vipinsh@google.com>

Use the constant-after-module-load kvm_ad_enabled() to check if SPTEs in
the TDP MMU need to be write-protected when clearing accessed/dirty status
instead of manually checking every SPTE.  The per-SPTE A/D enabling is
specific to nested EPT MMUs, i.e. when KVM is using EPT A/D bits but L1 is
not, and so cannot happen in the TDP MMU (which is non-nested only).

Keep the original code as sanity checks buried under MMU_WARN_ON().
MMU_WARN_ON() is more or less useless at the moment, but there are plans
to change that.

Link: https://lore.kernel.org/all/Yz4Qi7cn7TWTWQjj@google.com
Signed-off-by: Vipin Sharma <vipinsh@google.com>
[sean: split to separate patch, apply to dirty path, write changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7c25dbf32ecc..5a5642650c3e 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1621,7 +1621,10 @@ static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
 		if (!is_shadow_present_pte(iter.old_spte))
 			continue;
 
-		if (spte_ad_need_write_protect(iter.old_spte)) {
+		MMU_WARN_ON(kvm_ad_enabled() &&
+			    spte_ad_need_write_protect(iter.old_spte));
+
+		if (!kvm_ad_enabled()) {
 			if (is_writable_pte(iter.old_spte))
 				new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
 			else
@@ -1685,13 +1688,16 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root,
 		if (!mask)
 			break;
 
+		MMU_WARN_ON(kvm_ad_enabled() &&
+			    spte_ad_need_write_protect(iter.old_spte));
+
 		if (iter.level > PG_LEVEL_4K ||
 		    !(mask & (1UL << (iter.gfn - gfn))))
 			continue;
 
 		mask &= ~(1UL << (iter.gfn - gfn));
 
-		if (wrprot || spte_ad_need_write_protect(iter.old_spte)) {
+		if (wrprot || !kvm_ad_enabled()) {
 			if (is_writable_pte(iter.old_spte))
 				new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
 			else
-- 
2.40.0.rc2.332.ga46443480c-goog


  parent reply	other threads:[~2023-03-21 22:00 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-21 22:00 [PATCH v4 00/13] KVM: x86/mmu: Optimize clear dirty log Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 01/13] KVM: x86/mmu: Add a helper function to check if an SPTE needs atomic write Sean Christopherson
2023-03-21 22:00 ` Sean Christopherson [this message]
2023-03-21 22:00 ` [PATCH v4 03/13] KVM: x86/mmu: Consolidate Dirty vs. Writable clearing logic in TDP MMU Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 04/13] KVM: x86/mmu: Atomically clear SPTE dirty state in the clear-dirty-log flow Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 05/13] KVM: x86/mmu: Drop access tracking checks when clearing TDP MMU dirty bits Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 06/13] KVM: x86/mmu: Bypass __handle_changed_spte() " Sean Christopherson
2023-06-25  7:44   ` Like Xu
2023-06-26 21:37     ` Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 07/13] KVM: x86/mmu: Remove "record_dirty_log" in __tdp_mmu_set_spte() Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 08/13] KVM: x86/mmu: Clear only A-bit (if enabled) when aging TDP MMU SPTEs Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 09/13] KVM: x86/mmu: Drop unnecessary dirty log checks " Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 10/13] KVM: x86/mmu: Bypass __handle_changed_spte() " Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 11/13] KVM: x86/mmu: Remove "record_acc_track" in __tdp_mmu_set_spte() Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 12/13] KVM: x86/mmu: Remove handle_changed_spte_dirty_log() Sean Christopherson
2023-03-21 22:00 ` [PATCH v4 13/13] KVM: x86/mmu: Merge all handle_changed_pte*() functions Sean Christopherson
2023-03-31  0:13 ` [PATCH v4 00/13] KVM: x86/mmu: Optimize clear dirty log Vipin Sharma
2023-04-04 23:44 ` Sean Christopherson

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