KVM: VMX: Invert handling of CR0.WP for EPT without unrestricted guest

Opt-in to forcing CR0.WP=1 for shadow paging, and stop lying about WP
being "always on" for unrestricted guest.  In addition to making KVM a
wee bit more honest, this paves the way for additional cleanup.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-22-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -136,8 +136,7 @@ module_param(allow_smaller_maxphyaddr, bool, S_IRUGO);
 #define KVM_VM_CR0_ALWAYS_OFF (X86_CR0_NW | X86_CR0_CD)
 #define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST X86_CR0_NE
 #define KVM_VM_CR0_ALWAYS_ON				\
-	(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | 	\
-	 X86_CR0_WP | X86_CR0_PG | X86_CR0_PE)
+	(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
 
 #define KVM_VM_CR4_ALWAYS_ON_UNRESTRICTED_GUEST X86_CR4_VMXE
 #define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
@@ -2995,9 +2994,7 @@ void ept_save_pdptrs(struct kvm_vcpu *vcpu)
 	kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
 }
 
-static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
-					unsigned long cr0,
-					struct kvm_vcpu *vcpu)
+static void ept_update_paging_mode_cr0(unsigned long cr0, struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
@@ -3016,9 +3013,6 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
 		vcpu->arch.cr0 = cr0;
 		vmx_set_cr4(vcpu, kvm_read_cr4(vcpu));
 	}
-
-	if (!(cr0 & X86_CR0_WP))
-		*hw_cr0 &= ~X86_CR0_WP;
 }
 
 void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
@@ -3031,6 +3025,8 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 		hw_cr0 |= KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST;
 	else {
 		hw_cr0 |= KVM_VM_CR0_ALWAYS_ON;
+		if (!enable_ept)
+			hw_cr0 |= X86_CR0_WP;
 
 		if (vmx->rmode.vm86_active && (cr0 & X86_CR0_PE))
 			enter_pmode(vcpu);
@@ -3049,7 +3045,7 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 #endif
 
 	if (enable_ept && !is_unrestricted_guest(vcpu))
-		ept_update_paging_mode_cr0(&hw_cr0, cr0, vcpu);
+		ept_update_paging_mode_cr0(cr0, vcpu);
 
 	vmcs_writel(CR0_READ_SHADOW, cr0);
 	vmcs_writel(GUEST_CR0, hw_cr0);