[PATCH 1/6] KVM: SVM: allow to force AVIC to be enabled

Maxim Levitsky
2021-12-09T11:55:25Z

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>
---
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 dde0106ffc47..6fbce42b9776 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -206,6 +206,9 @@ 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);

@@ -1058,10 +1061,14 @@ 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);
}
--
2.26.3