linux-kernel - [PATCH 08/12] KVM: x86/mmu: Use IS_ENABLED() to avoid RETPOLINE for TDP page faults

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Date:   Sat, 23 Apr 2022 03:47:48 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Venkatesh Srinivas <venkateshs@...gle.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>
Subject: [PATCH 08/12] KVM: x86/mmu: Use IS_ENABLED() to avoid RETPOLINE for
 TDP page faults

Use IS_ENABLED() instead of an #ifdef to activate the anti-RETPOLINE fast
path for TDP page faults.  The generated code is identical, and the #ifdef
makes it dangerously difficult to extend the logic (guess who forgot to
add an "else" inside the #ifdef and ran through the page fault handler
twice).

No functional or binary change intented.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu_internal.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index c0c85cbfa159..9caa747ee033 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -248,10 +248,10 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		.req_level = PG_LEVEL_4K,
 		.goal_level = PG_LEVEL_4K,
 	};
-#ifdef CONFIG_RETPOLINE
-	if (fault.is_tdp)
+
+	if (IS_ENABLED(CONFIG_RETPOLINE) && fault.is_tdp)
 		return kvm_tdp_page_fault(vcpu, &fault);
-#endif
+
 	return vcpu->arch.mmu->page_fault(vcpu, &fault);
 }
 
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog