[Part2 PATCH v8 23/38] KVM: SVM: Add sev module_param

[Brijesh Singh <brijesh.singh@amd.com>]

The module parameter can be used to control the SEV feature support.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kvm/svm.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 7e46aea59615..59abb9fe2f13 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -284,6 +284,10 @@ module_param(vls, int, 0444);
 static int vgif = true;
 module_param(vgif, int, 0444);
 
+/* enable/disable SEV support */
+static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
+module_param(sev, int, 0444);
+
 static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
 static void svm_flush_tlb(struct kvm_vcpu *vcpu);
 static void svm_complete_interrupts(struct vcpu_svm *svm);
@@ -1049,6 +1053,15 @@ static int avic_ga_log_notifier(u32 ga_tag)
 	return 0;
 }
 
+/*
+ * Get the maximum number of encrypted guests:
+ *  Fn8001_001F[ECX][31:0]: Number of supported guests.
+ */
+static __init void sev_hardware_setup(void)
+{
+	max_sev_asid = cpuid_ecx(0x8000001F);
+}
+
 static __init int svm_hardware_setup(void)
 {
 	int cpu;
@@ -1084,6 +1097,16 @@ static __init int svm_hardware_setup(void)
 		kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE);
 	}
 
+	if (sev) {
+		if (boot_cpu_has(X86_FEATURE_SEV) &&
+		    IS_ENABLED(CONFIG_KVM_AMD_SEV)) {
+			sev_hardware_setup();
+			pr_info("SEV supported\n");
+		} else {
+			sev = false;
+		}
+	}
+
 	for_each_possible_cpu(cpu) {
 		r = svm_cpu_init(cpu);
 		if (r)
-- 
2.9.5