linux-kernel - [PATCH v3 14/25] KVM: VMX: Tweak the special handling of SECONDARY_EXEC_ENCLS_EXITING in setup_vmcs

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Date:   Fri,  8 Jul 2022 16:42:12 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     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: [PATCH v3 14/25] KVM: VMX: Tweak the special handling of SECONDARY_EXEC_ENCLS_EXITING in setup_vmcs_config()

SECONDARY_EXEC_ENCLS_EXITING is conditionally added to the 'optional'
checklist in setup_vmcs_config() but there's little value in doing so.
First, as the control is optional, we can always check for its
presence, no harm done. Second, the only real value cpu_has_sgx() check
gives is that on the CPUs which support SECONDARY_EXEC_ENCLS_EXITING but
don't support SGX, the control is not getting enabled. It's highly unlikely
such CPUs exist but it's possible that some hypervisors expose broken vCPU
models.

Preserve cpu_has_sgx() check but filter the result of adjust_vmx_controls()
instead of the input.

Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ce54f13d8da1..566be73c6509 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2528,9 +2528,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 			SECONDARY_EXEC_PT_CONCEAL_VMX |
 			SECONDARY_EXEC_ENABLE_VMFUNC |
 			SECONDARY_EXEC_BUS_LOCK_DETECTION |
-			SECONDARY_EXEC_NOTIFY_VM_EXITING;
-		if (cpu_has_sgx())
-			opt2 |= SECONDARY_EXEC_ENCLS_EXITING;
+			SECONDARY_EXEC_NOTIFY_VM_EXITING |
+			SECONDARY_EXEC_ENCLS_EXITING;
+
 		if (adjust_vmx_controls(min2, opt2,
 					MSR_IA32_VMX_PROCBASED_CTLS2,
 					&_cpu_based_2nd_exec_control) < 0)
@@ -2577,6 +2577,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 		vmx_cap->vpid = 0;
 	}
 
+	if (!cpu_has_sgx())
+		_cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_ENCLS_EXITING;
+
 	if (_cpu_based_exec_control & CPU_BASED_ACTIVATE_TERTIARY_CONTROLS) {
 		u64 opt3 = TERTIARY_EXEC_IPI_VIRT;
 
-- 
2.35.3