linux-kernel - Re: [PATCH v2 3/5] KVM: x86: Use common 'enable

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Date:   Mon, 24 May 2021 18:18:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Kechen Lu <kechenl@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] KVM: x86: Use common 'enable_apicv' variable for
 both APICv and AVIC

On 18/05/21 22:39, Sean Christopherson wrote:
>> +/* enable / disable AVIC */
>> +static int avic;
>> +module_param(avic, int, 0444);
> We should opportunistically make avic a "bool".
> 

And also:

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 11714c22c9f1..48cb498ff070 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -185,9 +185,12 @@ module_param(vls, int, 0444);
  static int vgif = true;
  module_param(vgif, int, 0444);
  
-/* enable / disable AVIC */
-static int avic;
-module_param(avic, int, 0444);
+/*
+ * enable / disable AVIC.  Because the defaults differ for APICv
+ * support between VMX and SVM we cannot use module_param_named.
+ */
+static bool avic;
+module_param(avic, bool, 0444);
  
  bool __read_mostly dump_invalid_vmcb;
  module_param(dump_invalid_vmcb, bool, 0644);
@@ -1013,11 +1016,7 @@ static __init int svm_hardware_setup(void)
  			nrips = false;
  	}
  
-	if (!npt_enabled || !boot_cpu_has(X86_FEATURE_AVIC))
-		avic = false;
-
-	/* 'enable_apicv' is common between VMX/SVM but the defaults differ */
-	enable_apicv = avic;
+	enable_apicv = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
  	if (enable_apicv) {
  		pr_info("AVIC enabled\n");
  

The "if" can come back when AVIC is enabled by default.

Paolo