[RESEND,16/30] KVM: x86: SVM: allow to force AVIC to be enabled

Commit Message

Maxim Levitsky Feb. 7, 2022, 3:54 p.m. UTC

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 <[e-mail]>
---
 arch/x86/kvm/svm/svm.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 85035324ed762..b88ca7f07a0fc 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -202,6 +202,9 @@  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);
 
@@ -4839,10 +4842,14 @@  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 {