linux-kernel - [PATCH] KVM: x86: Fix clang -Wimplicit-fallthrough in do_host

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Date:   Tue, 22 Mar 2022 08:29:06 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] KVM: x86: Fix clang -Wimplicit-fallthrough in do_host_cpuid()

Clang warns:

  arch/x86/kvm/cpuid.c:739:2: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
          default:
          ^
  arch/x86/kvm/cpuid.c:739:2: note: insert 'break;' to avoid fall-through
          default:
          ^
          break;
  1 error generated.

Clang is a little more pedantic than GCC, which does not warn when
falling through to a case that is just break or return. Clang's version
is more in line with the kernel's own stance in deprecated.rst, which
states that all switch/case blocks must end in either break,
fallthrough, continue, goto, or return. Add the missing break to silence
the warning.

Fixes: f144c49e8c39 ("KVM: x86: synthesize CPUID leaf 0x80000021h if useful")
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 arch/x86/kvm/cpuid.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 58b0b4e0263c..a3c87d2882ad 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -735,6 +735,7 @@ static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array,
 			if (function > READ_ONCE(max_cpuid_80000000))
 				return entry;
 		}
+		break;
 
 	default:
 		break;

base-commit: c9b8fecddb5bb4b67e351bbaeaa648a6f7456912
-- 
2.35.1