Re: [PATCH v3 6/7] KVM: x86: SVM: allow to force AVIC to be enabled

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On 3/1/22 15:36, Maxim Levitsky wrote:
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@xxxxxxxxxx>
---
  arch/x86/kvm/svm/svm.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 776585dd77769..a26b4c899899e 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);
@@ -4896,10 +4899,14 @@ 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 {

Queued, thanks.

Paolo



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