linux-kernel - [PATCH 01/22] KVM: x86/mmu: nested EPT cannot be used in SMM

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Date:   Thu, 14 Apr 2022 03:39:39 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com, David Matlack <dmatlack@...gle.com>
Subject: [PATCH 01/22] KVM: x86/mmu: nested EPT cannot be used in SMM

The role.base.smm flag is always zero when setting up shadow EPT,
do not bother copying it over from vcpu->arch.root_mmu.

Reviewed-by: David Matlack <dmatlack@...gle.com>
Reviewed-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c623019929a7..797c51bb6cda 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4910,9 +4910,11 @@ kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
 {
 	union kvm_mmu_role role = {0};
 
-	/* SMM flag is inherited from root_mmu */
-	role.base.smm = vcpu->arch.root_mmu.mmu_role.base.smm;
-
+	/*
+	 * KVM does not support SMM transfer monitors, and consequently does not
+	 * support the "entry to SMM" control either.  role.base.smm is always 0.
+	 */
+	WARN_ON_ONCE(is_smm(vcpu));
 	role.base.level = level;
 	role.base.has_4_byte_gpte = false;
 	role.base.direct = false;
-- 
2.31.1