linux-kernel - [PATCH] KVM: x86: Make enum conversion explicit in kvm_pdptr

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Message-Id: <20180226224224.244247-1-mka@chromium.org>
Date:   Mon, 26 Feb 2018 14:42:24 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Guenter Roeck <groeck@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH] KVM: x86: Make enum conversion explicit in kvm_pdptr_read()

The type 'enum kvm_reg_ex' is an extension of 'enum kvm_reg', however
the extension is only semantical and the compiler doesn't know about the
relationship between the two types. In kvm_pdptr_read() a value of the
extended type is passed to kvm_x86_ops->cache_reg(), which expects a
value of the base type. Clang raises the following warning about the
type mismatch:

arch/x86/kvm/kvm_cache_regs.h:44:32: warning: implicit conversion from
  enumeration type 'enum kvm_reg_ex' to different enumeration type
  'enum kvm_reg' [-Wenum-conversion]
    kvm_x86_ops->cache_reg(vcpu, VCPU_EXREG_PDPTR);

Cast VCPU_EXREG_PDPTR to 'enum kvm_reg' to make the compiler happy.

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
 arch/x86/kvm/kvm_cache_regs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index f500293dad8d..58ba12071014 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -41,7 +41,7 @@ static inline u64 kvm_pdptr_read(struct kvm_vcpu *vcpu, int index)
 
 	if (!test_bit(VCPU_EXREG_PDPTR,
 		      (unsigned long *)&vcpu->arch.regs_avail))
-		kvm_x86_ops->cache_reg(vcpu, VCPU_EXREG_PDPTR);
+		kvm_x86_ops->cache_reg(vcpu, (enum kvm_reg)VCPU_EXREG_PDPTR);
 
 	return vcpu->arch.walk_mmu->pdptrs[index];
 }
-- 
2.16.1.291.g4437f3f132-goog