KVM: Remove set_cr0_no_modeswitch() arch op

set_cr0_no_modeswitch() was a hack to avoid corrupting segment registers.
As we now cache the protected mode values on entry to real mode, this
isn't an issue anymore, and it interferes with reboot (which usually _is_
a modeswitch).
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/kvm.h

@@ -383,8 +383,6 @@ struct kvm_arch_ops {
 	void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l);
 	void (*decache_cr0_cr4_guest_bits)(struct kvm_vcpu *vcpu);
 	void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);
-	void (*set_cr0_no_modeswitch)(struct kvm_vcpu *vcpu,
-				      unsigned long cr0);
 	void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
 	void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);
 	void (*set_efer)(struct kvm_vcpu *vcpu, u64 efer);

drivers/kvm/kvm_main.c

@@ -1936,7 +1936,7 @@ static int kvm_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 	kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu);
 
 	mmu_reset_needed |= vcpu->cr0 != sregs->cr0;
-	kvm_arch_ops->set_cr0_no_modeswitch(vcpu, sregs->cr0);
+	kvm_arch_ops->set_cr0(vcpu, sregs->cr0);
 
 	mmu_reset_needed |= vcpu->cr4 != sregs->cr4;
 	kvm_arch_ops->set_cr4(vcpu, sregs->cr4);

drivers/kvm/svm.c

@@ -1716,7 +1716,6 @@ static struct kvm_arch_ops svm_arch_ops = {
 	.get_cs_db_l_bits = svm_get_cs_db_l_bits,
 	.decache_cr0_cr4_guest_bits = svm_decache_cr0_cr4_guest_bits,
 	.set_cr0 = svm_set_cr0,
-	.set_cr0_no_modeswitch = svm_set_cr0,
 	.set_cr3 = svm_set_cr3,
 	.set_cr4 = svm_set_cr4,
 	.set_efer = svm_set_efer,

drivers/kvm/vmx.c

@@ -788,22 +788,6 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	vcpu->cr0 = cr0;
 }
 
-/*
- * Used when restoring the VM to avoid corrupting segment registers
- */
-static void vmx_set_cr0_no_modeswitch(struct kvm_vcpu *vcpu, unsigned long cr0)
-{
-	if (!vcpu->rmode.active && !(cr0 & CR0_PE_MASK))
-		enter_rmode(vcpu);
-
-	vcpu->rmode.active = ((cr0 & CR0_PE_MASK) == 0);
-	update_exception_bitmap(vcpu);
-	vmcs_writel(CR0_READ_SHADOW, cr0);
-	vmcs_writel(GUEST_CR0,
-		    (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON);
-	vcpu->cr0 = cr0;
-}
-
 static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
 	vmcs_writel(GUEST_CR3, cr3);
@@ -2069,7 +2053,6 @@ static struct kvm_arch_ops vmx_arch_ops = {
 	.get_cs_db_l_bits = vmx_get_cs_db_l_bits,
 	.decache_cr0_cr4_guest_bits = vmx_decache_cr0_cr4_guest_bits,
 	.set_cr0 = vmx_set_cr0,
-	.set_cr0_no_modeswitch = vmx_set_cr0_no_modeswitch,
 	.set_cr3 = vmx_set_cr3,
 	.set_cr4 = vmx_set_cr4,
 #ifdef CONFIG_X86_64