linux-kernel - [PATCH v2 19/25] KVM: x86/mmu: simplify and/or inline computation of shadow MMU roles

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Date:   Mon, 21 Feb 2022 11:22:37 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     dmatlack@...gle.com, seanjc@...gle.com
Subject: [PATCH v2 19/25] KVM: x86/mmu: simplify and/or inline computation of shadow MMU roles

Shadow MMUs compute their role from cpu_mode.base, simply by adjusting
the root level.  It's one line of code, so do not place it in a separate
function.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c | 54 +++++++++++++++---------------------------
 1 file changed, 19 insertions(+), 35 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index d657e2e2ceec..47288643ab70 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4768,30 +4768,6 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
 	reset_tdp_shadow_zero_bits_mask(context);
 }
 
-static union kvm_mmu_page_role
-kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu,
-				   union kvm_mmu_paging_mode role)
-{
-	if (!role.ext.efer_lma)
-		role.base.level = PT32E_ROOT_LEVEL;
-	else if (role.ext.cr4_la57)
-		role.base.level = PT64_ROOT_5LEVEL;
-	else
-		role.base.level = PT64_ROOT_4LEVEL;
-
-	/*
-	 * KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role.
-	 * KVM uses NX when TDP is disabled to handle a variety of scenarios,
-	 * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
-	 * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
-	 * The iTLB multi-hit workaround can be toggled at any time, so assume
-	 * NX can be used by any non-nested shadow MMU to avoid having to reset
-	 * MMU contexts.
-	 */
-	role.base.efer_nx = true;
-	return role.base;
-}
-
 static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
 				    union kvm_mmu_paging_mode cpu_mode,
 				    union kvm_mmu_page_role root_role)
@@ -4822,18 +4798,23 @@ static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
 {
 	struct kvm_mmu *context = &vcpu->arch.root_mmu;
 	union kvm_mmu_paging_mode cpu_mode = kvm_calc_cpu_mode(vcpu, regs);
-	union kvm_mmu_page_role root_role =
-		kvm_calc_shadow_mmu_root_page_role(vcpu, cpu_mode);
+	union kvm_mmu_page_role root_role;
 
-	shadow_mmu_init_context(vcpu, context, cpu_mode, root_role);
-}
+	root_role = cpu_mode.base;
+	root_role.level = max_t(u32, root_role.level, PT32E_ROOT_LEVEL);
 
-static union kvm_mmu_page_role
-kvm_calc_shadow_npt_root_page_role(struct kvm_vcpu *vcpu,
-				   union kvm_mmu_paging_mode role)
-{
-	role.base.level = kvm_mmu_get_tdp_level(vcpu);
-	return role.base;
+	/*
+	 * KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role.
+	 * KVM uses NX when TDP is disabled to handle a variety of scenarios,
+	 * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
+	 * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
+	 * The iTLB multi-hit workaround can be toggled at any time, so assume
+	 * NX can be used by any non-nested shadow MMU to avoid having to reset
+	 * MMU contexts.
+	 */
+	root_role.efer_nx = true;
+
+	shadow_mmu_init_context(vcpu, context, cpu_mode, root_role);
 }
 
 void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
@@ -4846,7 +4827,10 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
 		.efer = efer,
 	};
 	union kvm_mmu_paging_mode cpu_mode = kvm_calc_cpu_mode(vcpu, &regs);
-	union kvm_mmu_page_role root_role = kvm_calc_shadow_npt_root_page_role(vcpu, cpu_mode);
+	union kvm_mmu_page_role root_role;
+
+	root_role = cpu_mode.base;
+	root_role.level = kvm_mmu_get_tdp_level(vcpu);
 
 	shadow_mmu_init_context(vcpu, context, cpu_mode, root_role);
 	kvm_mmu_new_pgd(vcpu, nested_cr3);
-- 
2.31.1