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From: Colin King <colin.king@canonical.com>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, kvm@vger.kernel.org,
	clang-built-linux@googlegroups.com
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: x86/mmu: fix comparison of u8 with -1
Date: Tue, 26 Nov 2019 16:12:55 +0000	[thread overview]
Message-ID: <20191126161255.323992-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.com>

The comparison of the u8 value __entry->u with -1 is always
going to be false because a __entry-u can never be negative.
Fix this by casting it to a s8 integer.

Addresses clang warning:
arch/x86/kvm/./mmutrace.h:360:16: warning: result of comparison
of constant -1 with expression of type 'u8' (aka 'unsigned char')
is always false [-Wtautological-constant-out-of-range-compare]

Fixes: 335e192a3fa4 ("KVM: x86: add tracepoints around __direct_map and FNAME(fetch)")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 arch/x86/kvm/mmutrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index 7ca8831c7d1a..3466cd528a67 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -357,7 +357,7 @@ TRACE_EVENT(
 		  __entry->r ? "r" : "-",
 		  __entry->spte & PT_WRITABLE_MASK ? "w" : "-",
 		  __entry->x ? "x" : "-",
-		  __entry->u == -1 ? "" : (__entry->u ? "u" : "-"),
+		  (s8)__entry->u == -1 ? "" : (__entry->u ? "u" : "-"),
 		  __entry->level, __entry->sptep
 	)
 );
-- 
2.24.0


WARNING: multiple messages have this Message-ID (diff)
From: Colin King <colin.king@canonical.com>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, kvm@vger.kernel.org,
	clang-built-linux@googlegroups.com
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: x86/mmu: fix comparison of u8 with -1
Date: Tue, 26 Nov 2019 16:12:55 +0000	[thread overview]
Message-ID: <20191126161255.323992-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.com>

The comparison of the u8 value __entry->u with -1 is always
going to be false because a __entry-u can never be negative.
Fix this by casting it to a s8 integer.

Addresses clang warning:
arch/x86/kvm/./mmutrace.h:360:16: warning: result of comparison
of constant -1 with expression of type 'u8' (aka 'unsigned char')
is always false [-Wtautological-constant-out-of-range-compare]

Fixes: 335e192a3fa4 ("KVM: x86: add tracepoints around __direct_map and FNAME(fetch)")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 arch/x86/kvm/mmutrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index 7ca8831c7d1a..3466cd528a67 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -357,7 +357,7 @@ TRACE_EVENT(
 		  __entry->r ? "r" : "-",
 		  __entry->spte & PT_WRITABLE_MASK ? "w" : "-",
 		  __entry->x ? "x" : "-",
-		  __entry->u = -1 ? "" : (__entry->u ? "u" : "-"),
+		  (s8)__entry->u = -1 ? "" : (__entry->u ? "u" : "-"),
 		  __entry->level, __entry->sptep
 	)
 );
-- 
2.24.0

             reply	other threads:[~2019-11-26 16:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-26 16:12 Colin King [this message]
2019-11-26 16:12 ` [PATCH] KVM: x86/mmu: fix comparison of u8 with -1 Colin King
2019-11-26 17:24 ` Nick Desaulniers
2019-11-26 17:24   ` Nick Desaulniers
2019-11-27  2:21 linmiaohe
2019-11-27  2:21 ` linmiaohe

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