KVM: x86: Use KVM cpu caps to track UMIP emulation

Set UMIP in kvm_cpu_caps when it is emulated by VMX, even though the
bit will effectively be dropped by do_host_cpuid().  This allows
checking for UMIP emulation via kvm_cpu_caps instead of a dedicated
kvm_x86_ops callback.

No functional change intended.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1177,7 +1177,6 @@ struct kvm_x86_ops {
 	void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
 		enum exit_fastpath_completion *exit_fastpath);
 
-	bool (*umip_emulated)(void);
 	bool (*pt_supported)(void);
 
 	int (*check_nested_events)(struct kvm_vcpu *vcpu);

arch/x86/kvm/svm.c

@@ -6088,11 +6088,6 @@ static bool svm_rdtscp_supported(void)
 	return boot_cpu_has(X86_FEATURE_RDTSCP);
 }
 
-static bool svm_umip_emulated(void)
-{
-	return false;
-}
-
 static bool svm_pt_supported(void)
 {
 	return false;
@@ -7460,7 +7455,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.cpuid_update = svm_cpuid_update,
 
 	.rdtscp_supported = svm_rdtscp_supported,
-	.umip_emulated = svm_umip_emulated,
 	.pt_supported = svm_pt_supported,
 
 	.set_supported_cpuid = svm_set_supported_cpuid,

arch/x86/kvm/vmx/vmx.c

@@ -7132,6 +7132,10 @@ static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
 {
 	switch (entry->function) {
 	case 0x7:
+		/*
+		 * UMIP needs to be manually set even though vmx_set_cpu_caps()
+		 * also sets UMIP since do_host_cpuid() will drop it.
+		 */
 		if (vmx_umip_emulated())
 			cpuid_entry_set(entry, X86_FEATURE_UMIP);
 		break;
@@ -7160,6 +7164,9 @@ static __init void vmx_set_cpu_caps(void)
 	if (enable_ept && boot_cpu_has(X86_FEATURE_OSPKE))
 		kvm_cpu_cap_check_and_set(X86_FEATURE_PKU);
 
+	if (vmx_umip_emulated())
+		kvm_cpu_cap_set(X86_FEATURE_UMIP);
+
 	/* CPUID 0xD.1 */
 	if (!vmx_xsaves_supported())
 		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
@@ -7963,7 +7970,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 
 	.check_intercept = vmx_check_intercept,
 	.handle_exit_irqoff = vmx_handle_exit_irqoff,
-	.umip_emulated = vmx_umip_emulated,
 	.pt_supported = vmx_pt_supported,
 
 	.request_immediate_exit = vmx_request_immediate_exit,

arch/x86/kvm/x86.c

@@ -928,7 +928,7 @@ static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
 	if (kvm_cpu_cap_has(X86_FEATURE_LA57))
 		reserved_bits &= ~X86_CR4_LA57;
 
-	if (kvm_x86_ops->umip_emulated())
+	if (kvm_cpu_cap_has(X86_FEATURE_UMIP))
 		reserved_bits &= ~X86_CR4_UMIP;
 
 	return reserved_bits;