KVM: x86: SVM: allow to force AVIC to be enabled

Apparently on some systems AVIC is disabled in CPUID but still usable.

Allow the user to override the CPUID if the user is willing to
take the risk.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220301143650.143749-7-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index af1706144bacd8f1d5301586ecc1a3daea52156c..f1cb8e9917493eb2a36cdc89ae8701e80b38899e 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -189,6 +189,9 @@ module_param(tsc_scaling, int, 0444);
 static bool avic;
 module_param(avic, bool, 0444);
 
+static bool force_avic;
+module_param_unsafe(force_avic, bool, 0444);
+
 bool __read_mostly dump_invalid_vmcb;
 module_param(dump_invalid_vmcb, bool, 0644);
 
@@ -4813,10 +4816,14 @@ static __init int svm_hardware_setup(void)
                        nrips = false;
        }
 
-       enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
+       enable_apicv = avic = avic && npt_enabled && (boot_cpu_has(X86_FEATURE_AVIC) || force_avic);
 
        if (enable_apicv) {
-               pr_info("AVIC enabled\n");
+               if (!boot_cpu_has(X86_FEATURE_AVIC)) {
+                       pr_warn("AVIC is not supported in CPUID but force enabled");
+                       pr_warn("Your system might crash and burn");
+               } else
+                       pr_info("AVIC enabled\n");
 
                amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
        } else {