[PATCH v4 07/20] KVM: x86/mmu: Move guest PT write-protection to account_shadowed()

From: David Matlack <dmatlack@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	"open list:KERNEL VIRTUAL MACHINE FOR MIPS \(KVM/mips\)"
	<kvm@vger.kernel.org>, Marc Zyngier <maz@kernel.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	"open list:KERNEL VIRTUAL MACHINE FOR MIPS \(KVM/mips\)"
	<linux-mips@vger.kernel.org>, David Matlack <dmatlack@google.com>,
	Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	"open list:KERNEL VIRTUAL MACHINE FOR RISC-V \(KVM/riscv\)"
	<kvm-riscv@lists.infradead.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Ben Gardon <bgardon@google.com>,
	maciej.szmigiero@oracle.com,
	"moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 \(KVM/arm64\)"
	<kvmarm@lists.cs.columbia.edu>, Peter Feiner <pfeiner@google.com>
Subject: [PATCH v4 07/20] KVM: x86/mmu: Move guest PT write-protection to account_shadowed()
Date: Fri, 22 Apr 2022 21:05:33 +0000	[thread overview]
Message-ID: <20220422210546.458943-8-dmatlack@google.com> (raw)
In-Reply-To: <20220422210546.458943-1-dmatlack@google.com>

Move the code that write-protects newly-shadowed guest page tables into
account_shadowed(). This avoids a extra gfn-to-memslot lookup and is a
more logical place for this code to live. But most importantly, this
reduces kvm_mmu_alloc_shadow_page()'s reliance on having a struct
kvm_vcpu pointer, which will be necessary when creating new shadow pages
during VM ioctls for eager page splitting.

Note, it is safe to drop the role.level == PG_LEVEL_4K check since
account_shadowed() returns early if role.level > PG_LEVEL_4K.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index fa7846760887..4f894db88bbf 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -807,6 +807,9 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
 						    KVM_PAGE_TRACK_WRITE);
 
 	kvm_mmu_gfn_disallow_lpage(slot, gfn);
+
+	if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K))
+		kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
 }
 
 void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
@@ -2100,11 +2103,9 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm_vcpu *vcpu,
 	sp->gfn = gfn;
 	sp->role = role;
 	hlist_add_head(&sp->hash_link, sp_list);
-	if (!role.direct) {
+
+	if (!role.direct)
 		account_shadowed(vcpu->kvm, sp);
-		if (role.level == PG_LEVEL_4K && kvm_vcpu_write_protect_gfn(vcpu, gfn))
-			kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn, 1);
-	}
 
 	return sp;
 }
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog

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