linux-kernel - [PATCH 16/22] kvm: x86/mmu: Support changed pte notifier in tdp MMU

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Message-Id: <20201023163024.2765558-17-pbonzini@redhat.com>
Date:   Fri, 23 Oct 2020 12:30:18 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     bgardon@...gle.com
Subject: [PATCH 16/22] kvm: x86/mmu: Support changed pte notifier in tdp MMU

From: Ben Gardon <bgardon@...gle.com>

In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
a hook and handle the change_pte MMU notifier.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
	https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538

Signed-off-by: Ben Gardon <bgardon@...gle.com>
Message-Id: <20201014182700.2888246-15-bgardon@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c     |  9 +++++-
 arch/x86/kvm/mmu/tdp_mmu.c | 56 ++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/mmu/tdp_mmu.h |  3 ++
 3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 33ec6c4c36d7..41f0354c7489 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1509,7 +1509,14 @@ int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end,
 
 int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
 {
-	return kvm_handle_hva(kvm, hva, (unsigned long)&pte, kvm_set_pte_rmapp);
+	int r;
+
+	r = kvm_handle_hva(kvm, hva, (unsigned long)&pte, kvm_set_pte_rmapp);
+
+	if (kvm->arch.tdp_mmu_enabled)
+		r |= kvm_tdp_mmu_set_spte_hva(kvm, hva, &pte);
+
+	return r;
 }
 
 static int kvm_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index dd6b8a8f1c93..64e640cfcff9 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -671,3 +671,59 @@ int kvm_tdp_mmu_test_age_hva(struct kvm *kvm, unsigned long hva)
 	return kvm_tdp_mmu_handle_hva_range(kvm, hva, hva + 1, 0,
 					    test_age_gfn);
 }
+
+/*
+ * Handle the changed_pte MMU notifier for the TDP MMU.
+ * data is a pointer to the new pte_t mapping the HVA specified by the MMU
+ * notifier.
+ * Returns non-zero if a flush is needed before releasing the MMU lock.
+ */
+static int set_tdp_spte(struct kvm *kvm, struct kvm_memory_slot *slot,
+			struct kvm_mmu_page *root, gfn_t gfn, gfn_t unused,
+			unsigned long data)
+{
+	struct tdp_iter iter;
+	pte_t *ptep = (pte_t *)data;
+	kvm_pfn_t new_pfn;
+	u64 new_spte;
+	int need_flush = 0;
+
+	WARN_ON(pte_huge(*ptep));
+
+	new_pfn = pte_pfn(*ptep);
+
+	tdp_root_for_each_pte(iter, root, gfn, gfn + 1) {
+		if (iter.level != PG_LEVEL_4K)
+			continue;
+
+		if (!is_shadow_present_pte(iter.old_spte))
+			break;
+
+		tdp_mmu_set_spte(kvm, &iter, 0);
+
+		kvm_flush_remote_tlbs_with_address(kvm, iter.gfn, 1);
+
+		if (!pte_write(*ptep)) {
+			new_spte = kvm_mmu_changed_pte_notifier_make_spte(
+					iter.old_spte, new_pfn);
+
+			tdp_mmu_set_spte(kvm, &iter, new_spte);
+		}
+
+		need_flush = 1;
+	}
+
+	if (need_flush)
+		kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
+
+	return 0;
+}
+
+int kvm_tdp_mmu_set_spte_hva(struct kvm *kvm, unsigned long address,
+			     pte_t *host_ptep)
+{
+	return kvm_tdp_mmu_handle_hva_range(kvm, address, address + 1,
+					    (unsigned long)host_ptep,
+					    set_tdp_spte);
+}
+
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index ddc1bf12d0fc..aeee3ce7b3f4 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -25,4 +25,7 @@ int kvm_tdp_mmu_zap_hva_range(struct kvm *kvm, unsigned long start,
 int kvm_tdp_mmu_age_hva_range(struct kvm *kvm, unsigned long start,
 			      unsigned long end);
 int kvm_tdp_mmu_test_age_hva(struct kvm *kvm, unsigned long hva);
+
+int kvm_tdp_mmu_set_spte_hva(struct kvm *kvm, unsigned long address,
+			     pte_t *host_ptep);
 #endif /* __KVM_X86_MMU_TDP_MMU_H */
-- 
2.26.2