[PATCH] KVM: Fix warning in emulator_cmpxchg_emulated

[PATCH] KVM: Fix warning in emulator_cmpxchg_emulated

[Sasha Levin]

Make sure 'exchanged' is initialized. Fixes the following warning:

arch/x86/kvm/x86.c: In function 'emulator_cmpxchg_emulated':
arch/x86/kvm/x86.c:3794:7: warning: 'exchanged' may be used uninitialized in this function

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 arch/x86/kvm/x86.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eeeaf2e..9338afc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3791,7 +3791,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
 	gpa_t gpa;
 	struct page *page;
 	char *kaddr;
-	bool exchanged;
+	bool exchanged = false;
 
 	/* guests cmpxchg8b have to be emulated atomically */
 	if (bytes > 8 || (bytes & (bytes - 1)))
-- 
1.7.8

Re: [PATCH] KVM: Fix warning in emulator_cmpxchg_emulated

[Jan Kiszka]

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On 2011-12-08 07:17, Sasha Levin wrote:
> Make sure 'exchanged' is initialized. Fixes the following warning:
> 
> arch/x86/kvm/x86.c: In function 'emulator_cmpxchg_emulated':
> arch/x86/kvm/x86.c:3794:7: warning: 'exchanged' may be used uninitialized in this function
> 
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
>  arch/x86/kvm/x86.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index eeeaf2e..9338afc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3791,7 +3791,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
>  	gpa_t gpa;
>  	struct page *page;
>  	char *kaddr;
> -	bool exchanged;
> +	bool exchanged = false;
>  
>  	/* guests cmpxchg8b have to be emulated atomically */
>  	if (bytes > 8 || (bytes & (bytes - 1)))

Isn't BUG() tagged as no-return in the kernel? Because this
initialization is obviously unneeded.

Jan


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Re: [PATCH] KVM: Fix warning in emulator_cmpxchg_emulated

[Sasha Levin]

On Thu, 2011-12-08 at 09:04 +0100, Jan Kiszka wrote:
> On 2011-12-08 07:17, Sasha Levin wrote:
> > Make sure 'exchanged' is initialized. Fixes the following warning:
> > 
> > arch/x86/kvm/x86.c: In function 'emulator_cmpxchg_emulated':
> > arch/x86/kvm/x86.c:3794:7: warning: 'exchanged' may be used uninitialized in this function
> > 
> > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> > ---
> >  arch/x86/kvm/x86.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index eeeaf2e..9338afc 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -3791,7 +3791,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> >  	gpa_t gpa;
> >  	struct page *page;
> >  	char *kaddr;
> > -	bool exchanged;
> > +	bool exchanged = false;
> >  
> >  	/* guests cmpxchg8b have to be emulated atomically */
> >  	if (bytes > 8 || (bytes & (bytes - 1)))
> 
> Isn't BUG() tagged as no-return in the kernel? Because this
> initialization is obviously unneeded.

It looks like __builtin_unreachable() requires a gcc newer than mine.

-- 

Sasha.