linux-kernel - [PATCH 26/54] KVM: x86/mmu: Do not set paging-related bits in MMU role if CR0.PG=0

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Date:   Tue, 22 Jun 2021 10:57:11 -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 26/54] KVM: x86/mmu: Do not set paging-related bits in MMU
 role if CR0.PG=0

Don't set CR0/CR4/EFER bits in the MMU role if paging is disabled, paging
modifiers are irrelevant if there is no paging in the first place.
Somewhat arbitrarily clear gpte_is_8_bytes for shadow paging if paging is
disabled in the guest.  Again, there are no guest PTEs to process, so the
size is meaningless.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index be95595b30c7..0eb77a45f1ff 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4568,13 +4568,15 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu,
 {
 	union kvm_mmu_extended_role ext = {0};
 
-	ext.cr0_pg = ____is_cr0_pg(regs);
-	ext.cr4_pae = ____is_cr4_pae(regs);
-	ext.cr4_smep = ____is_cr4_smep(regs);
-	ext.cr4_smap = ____is_cr4_smap(regs);
-	ext.cr4_pse = ____is_cr4_pse(regs);
-	ext.cr4_pke = ____is_cr4_pke(regs);
-	ext.cr4_la57 = ____is_cr4_la57(regs);
+	if (____is_cr0_pg(regs)) {
+		ext.cr0_pg = 1;
+		ext.cr4_pae = ____is_cr4_pae(regs);
+		ext.cr4_smep = ____is_cr4_smep(regs);
+		ext.cr4_smap = ____is_cr4_smap(regs);
+		ext.cr4_pse = ____is_cr4_pse(regs);
+		ext.cr4_pke = ____is_cr4_pke(regs);
+		ext.cr4_la57 = ____is_cr4_la57(regs);
+	}
 
 	ext.valid = 1;
 
@@ -4588,8 +4590,10 @@ static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
 	union kvm_mmu_role role = {0};
 
 	role.base.access = ACC_ALL;
-	role.base.efer_nx = ____is_efer_nx(regs);
-	role.base.cr0_wp = ____is_cr0_wp(regs);
+	if (____is_cr0_pg(regs)) {
+		role.base.efer_nx = ____is_efer_nx(regs);
+		role.base.cr0_wp = ____is_cr0_wp(regs);
+	}
 	role.base.smm = is_smm(vcpu);
 	role.base.guest_mode = is_guest_mode(vcpu);
 
@@ -4680,7 +4684,7 @@ kvm_calc_shadow_root_page_role_common(struct kvm_vcpu *vcpu,
 
 	role.base.smep_andnot_wp = role.ext.cr4_smep && !____is_cr0_wp(regs);
 	role.base.smap_andnot_wp = role.ext.cr4_smap && !____is_cr0_wp(regs);
-	role.base.gpte_is_8_bytes = ____is_cr4_pae(regs);
+	role.base.gpte_is_8_bytes = ____is_cr0_pg(regs) && ____is_cr4_pae(regs);
 
 	return role;
 }
-- 
2.32.0.288.g62a8d224e6-goog