linux-kernel - [PATCH 42/54] KVM: x86/mmu: Don't update nested guest's paging bitmasks if CR0.PG=0

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Date:   Tue, 22 Jun 2021 10:57:27 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 42/54] KVM: x86/mmu: Don't update nested guest's paging
 bitmasks if CR0.PG=0

Don't bother updating the bitmasks and last-leaf information if paging is
disabled as the metadata will never be used.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 52311c2efd5d..30eb1364fc20 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4646,12 +4646,12 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 		context->gva_to_gpa = paging32_gva_to_gpa;
 	}
 
-	if (is_cr0_pg(context))
+	if (is_cr0_pg(context)) {
 		reset_rsvds_bits_mask(vcpu, context);
-
-	update_permission_bitmask(context, false);
-	update_pkru_bitmask(context);
-	update_last_nonleaf_level(context);
+		update_permission_bitmask(context, false);
+		update_pkru_bitmask(context);
+		update_last_nonleaf_level(context);
+	}
 	reset_tdp_shadow_zero_bits_mask(vcpu, context);
 }
 
@@ -4899,12 +4899,12 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
 	else
 		g_context->gva_to_gpa = paging32_gva_to_gpa_nested;
 
-	if (is_cr0_pg(g_context))
+	if (is_cr0_pg(g_context)) {
 		reset_rsvds_bits_mask(vcpu, g_context);
-
-	update_permission_bitmask(g_context, false);
-	update_pkru_bitmask(g_context);
-	update_last_nonleaf_level(g_context);
+		update_permission_bitmask(g_context, false);
+		update_pkru_bitmask(g_context);
+		update_last_nonleaf_level(g_context);
+	}
 }
 
 void kvm_init_mmu(struct kvm_vcpu *vcpu)
-- 
2.32.0.288.g62a8d224e6-goog