x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed

MMU reconfiguration in init_kvm_tdp_mmu()/kvm_init_shadow_mmu() can be
avoided if the source data used to configure it didn't change; enhance
MMU extended role with the required fields and consolidate common code in
kvm_calc_mmu_role_common().

Signed-off-by: Vitaly Kuznetsov <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: vittyvk

arch/x86/include/asm/kvm_host.h

@@ -293,10 +293,12 @@ union kvm_mmu_extended_role {
 	struct {
 		unsigned int valid:1;
 		unsigned int execonly:1;
+		unsigned int cr0_pg:1;
 		unsigned int cr4_pse:1;
 		unsigned int cr4_pke:1;
 		unsigned int cr4_smap:1;
 		unsigned int cr4_smep:1;
+		unsigned int cr4_la57:1;
 	};
 };
 

arch/x86/kvm/mmu.c

@@ -4728,37 +4728,61 @@ 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_paging(vcpu);
 	ext.cr4_smep = !!kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
 	ext.cr4_smap = !!kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
 	ext.cr4_pse = !!is_pse(vcpu);
 	ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
+	ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
 
 	ext.valid = 1;
 
 	return ext;
 }
 
-static union kvm_mmu_page_role
-kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu)
+static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
+						   bool base_only)
+{
+	union kvm_mmu_role role = {0};
+
+	role.base.access = ACC_ALL;
+	role.base.nxe = !!is_nx(vcpu);
+	role.base.cr4_pae = !!is_pae(vcpu);
+	role.base.cr0_wp = is_write_protection(vcpu);
+	role.base.smm = is_smm(vcpu);
+	role.base.guest_mode = is_guest_mode(vcpu);
+
+	if (base_only)
+		return role;
+
+	role.ext = kvm_calc_mmu_role_ext(vcpu);
+
+	return role;
+}
+
+static union kvm_mmu_role
+kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
 {
-	union kvm_mmu_page_role role = {0};
+	union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, base_only);
 
-	role.guest_mode = is_guest_mode(vcpu);
-	role.smm = is_smm(vcpu);
-	role.ad_disabled = (shadow_accessed_mask == 0);
-	role.level = kvm_x86_ops->get_tdp_level(vcpu);
-	role.direct = true;
-	role.access = ACC_ALL;
+	role.base.ad_disabled = (shadow_accessed_mask == 0);
+	role.base.level = kvm_x86_ops->get_tdp_level(vcpu);
+	role.base.direct = true;
 
 	return role;
 }
 
 static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu *context = vcpu->arch.mmu;
+	union kvm_mmu_role new_role =
+		kvm_calc_tdp_mmu_root_page_role(vcpu, false);
 
-	context->mmu_role.base.word = mmu_base_role_mask.word &
-				  kvm_calc_tdp_mmu_root_page_role(vcpu).word;
+	new_role.base.word &= mmu_base_role_mask.word;
+	if (new_role.as_u64 == context->mmu_role.as_u64)
+		return;
+
+	context->mmu_role.as_u64 = new_role.as_u64;
 	context->page_fault = tdp_page_fault;
 	context->sync_page = nonpaging_sync_page;
 	context->invlpg = nonpaging_invlpg;
@@ -4798,36 +4822,36 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 	reset_tdp_shadow_zero_bits_mask(vcpu, context);
 }
 
-static union kvm_mmu_page_role
-kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu)
-{
-	union kvm_mmu_page_role role = {0};
-	bool smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
-	bool smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
-
-	role.nxe = is_nx(vcpu);
-	role.cr4_pae = !!is_pae(vcpu);
-	role.cr0_wp  = is_write_protection(vcpu);
-	role.smep_andnot_wp = smep && !is_write_protection(vcpu);
-	role.smap_andnot_wp = smap && !is_write_protection(vcpu);
-	role.guest_mode = is_guest_mode(vcpu);
-	role.smm = is_smm(vcpu);
-	role.direct = !is_paging(vcpu);
-	role.access = ACC_ALL;
+static union kvm_mmu_role
+kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
+{
+	union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, base_only);
+
+	role.base.smep_andnot_wp = role.ext.cr4_smep &&
+		!is_write_protection(vcpu);
+	role.base.smap_andnot_wp = role.ext.cr4_smap &&
+		!is_write_protection(vcpu);
+	role.base.direct = !is_paging(vcpu);
 
 	if (!is_long_mode(vcpu))
-		role.level = PT32E_ROOT_LEVEL;
+		role.base.level = PT32E_ROOT_LEVEL;
 	else if (is_la57_mode(vcpu))
-		role.level = PT64_ROOT_5LEVEL;
+		role.base.level = PT64_ROOT_5LEVEL;
 	else
-		role.level = PT64_ROOT_4LEVEL;
+		role.base.level = PT64_ROOT_4LEVEL;
 
 	return role;
 }
 
 void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu *context = vcpu->arch.mmu;
+	union kvm_mmu_role new_role =
+		kvm_calc_shadow_mmu_root_page_role(vcpu, false);
+
+	new_role.base.word &= mmu_base_role_mask.word;
+	if (new_role.as_u64 == context->mmu_role.as_u64)
+		return;
 
 	if (!is_paging(vcpu))
 		nonpaging_init_context(vcpu, context);
@@ -4838,8 +4862,7 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
 	else
 		paging32_init_context(vcpu, context);
 
-	context->mmu_role.base.word = mmu_base_role_mask.word &
-				  kvm_calc_shadow_mmu_root_page_role(vcpu).word;
+	context->mmu_role.as_u64 = new_role.as_u64;
 	reset_shadow_zero_bits_mask(vcpu, context);
 }
 EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
@@ -4977,10 +5000,14 @@ EXPORT_SYMBOL_GPL(kvm_init_mmu);
 static union kvm_mmu_page_role
 kvm_mmu_calc_root_page_role(struct kvm_vcpu *vcpu)
 {
+	union kvm_mmu_role role;
+
 	if (tdp_enabled)
-		return kvm_calc_tdp_mmu_root_page_role(vcpu);
+		role = kvm_calc_tdp_mmu_root_page_role(vcpu, true);
 	else
-		return kvm_calc_shadow_mmu_root_page_role(vcpu);
+		role = kvm_calc_shadow_mmu_root_page_role(vcpu, true);
+
+	return role.base;
 }
 
 void kvm_mmu_reset_context(struct kvm_vcpu *vcpu)