linux-kernel - Re: [PATCH v4 09/25] KVM: VMX: nVMX: Support TSC scaling and PERF_GLOBAL

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Message-ID: <870d507d-a516-5601-4d21-2bfd571cf008@redhat.com>
Date:   Thu, 28 Jul 2022 23:52:05 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 09/25] KVM: VMX: nVMX: Support TSC scaling and
 PERF_GLOBAL_CTRL with enlightened VMCS

On 7/25/22 20:18, Sean Christopherson wrote:
>> I kind of like the idea of having a two-dimensional array based on the enums
>> instead of switch statements, so for now I'll keep Vitaly's enums.
> I don't have a strong opinion on using a 2d array, but unless I'm missing something,
> that's nowhere to be found in this patch.  IMO, having the enums without them
> providing any unique value is silly and obfuscates the code.

Yeah, like this:

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index d8da4026c93d..8055128d8638 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -342,9 +342,10 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
  	return 0;
  }
  
-enum evmcs_v1_revision {
+enum evmcs_revision {
  	EVMCSv1_2016,
  	EVMCSv1_2022,
+	EVMCS_REVISION_MAX,
  };
  
  enum evmcs_unsupported_ctrl_type {
@@ -353,13 +354,37 @@ enum evmcs_unsupported_ctrl_type {
  	EVMCS_2NDEXEC,
  	EVMCS_PINCTRL,
  	EVMCS_VMFUNC,
+	EVMCS_CTRL_MAX,
+};
+
+static u32 evmcs_unsupported_ctls[EVMCS_CTRL_MAX][EVMCS_REVISION_MAX] = {
+	[EVMCS_EXIT_CTLS] = {
+		[EVMCSv1_2016] = EVMCS1_UNSUPPORTED_VMEXIT_CTRL | VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL,
+		[EVMCSv1_2022] = EVMCS1_UNSUPPORTED_VMEXIT_CTRL,
+	},
+	[EVMCS_ENTRY_CTLS] = {
+		[EVMCSv1_2016] = EVMCS1_UNSUPPORTED_VMENTRY_CTRL | VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL,
+		[EVMCSv1_2022] =  EVMCS1_UNSUPPORTED_VMENTRY_CTRL,
+	},
+	[EVMCS_2NDEXEC] = {
+		[EVMCSv1_2016] = EVMCS1_UNSUPPORTED_2NDEXEC | SECONDARY_EXEC_TSC_SCALING,
+		[EVMCSv1_2022] = EVMCS1_UNSUPPORTED_2NDEXEC,
+	},
+	[EVMCS_PINCTRL] = {
+		[EVMCSv1_2016] = EVMCS1_UNSUPPORTED_PINCTRL,
+		[EVMCSv1_2022] = EVMCS1_UNSUPPORTED_PINCTRL,
+	},
+	[EVMCS_VMFUNC] = {
+		[EVMCSv1_2016] = EVMCS1_UNSUPPORTED_VMFUNC,
+		[EVMCSv1_2022] = EVMCS1_UNSUPPORTED_VMFUNC,
+	},
  };
  
  static u32 evmcs_get_unsupported_ctls(struct kvm_vcpu *vcpu,
  				      enum evmcs_unsupported_ctrl_type ctrl_type)
  {
  	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
-	enum evmcs_v1_revision evmcs_rev = EVMCSv1_2016;
+	enum evmcs_revision evmcs_rev = EVMCSv1_2016;
  
  	if (!hv_vcpu)
  		return 0;
@@ -367,32 +392,7 @@ static u32 evmcs_get_unsupported_ctls(struct kvm_vcpu *vcpu,
  	if (hv_vcpu->cpuid_cache.nested_ebx & HV_X64_NESTED_EVMCS1_2022_UPDATE)
  		evmcs_rev = EVMCSv1_2022;
  
-	switch (ctrl_type) {
-	case EVMCS_EXIT_CTLS:
-		if (evmcs_rev == EVMCSv1_2016)
-			return EVMCS1_UNSUPPORTED_VMEXIT_CTRL |
-				VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
-		else
-			return EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
-	case EVMCS_ENTRY_CTLS:
-		if (evmcs_rev == EVMCSv1_2016)
-			return EVMCS1_UNSUPPORTED_VMENTRY_CTRL |
-				VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
-		else
-			return EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
-	case EVMCS_2NDEXEC:
-		if (evmcs_rev == EVMCSv1_2016)
-			return EVMCS1_UNSUPPORTED_2NDEXEC |
-				SECONDARY_EXEC_TSC_SCALING;
-		else
-			return EVMCS1_UNSUPPORTED_2NDEXEC;
-	case EVMCS_PINCTRL:
-		return EVMCS1_UNSUPPORTED_PINCTRL;
-	case EVMCS_VMFUNC:
-		return EVMCS1_UNSUPPORTED_VMFUNC;
-	}
-
-	return 0;
+	return evmcs_unsupported_ctls[ctrl_type][evmcs_rev];
  }
  
  void nested_evmcs_filter_control_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)

Paolo