linux-next: kvm tree build warning

linux-next: kvm tree build warning

[Stephen Rothwell]

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Hi Avi,

Today's linux-next build (x86_64_allmodconfig) produced this warning:

arch/x86/kvm/lapic.c: In function 'apic_mmio_write':
arch/x86/kvm/lapic.c:834: warning: 'return' with no value, in function returning non-void

Introduced by commit 55b23c7377c9f9f0b4a4b90950f0e18b26ac45e8 ("KVM:
x2apic interface to lapic").

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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Re: linux-next: kvm tree build warning

[Gleb Natapov]

On Mon, Jul 06, 2009 at 11:37:52AM +1000, Stephen Rothwell wrote:
> Hi Avi,
> 
> Today's linux-next build (x86_64_allmodconfig) produced this warning:
> 
> arch/x86/kvm/lapic.c: In function 'apic_mmio_write':
> arch/x86/kvm/lapic.c:834: warning: 'return' with no value, in function returning non-void
> 
> Introduced by commit 55b23c7377c9f9f0b4a4b90950f0e18b26ac45e8 ("KVM:
> x2apic interface to lapic").
> 
Yes sorry. I see that Sheng Yang already posted the fix.

--
			Gleb.

Re: linux-next: kvm tree build warning

[Stephen Rothwell]

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Hi Gleb,

On Mon, 6 Jul 2009 08:28:55 +0300 Gleb Natapov <gleb@redhat.com> wrote:
>
> Yes sorry. I see that Sheng Yang already posted the fix.

Thanks.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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linux-next: kvm tree build warning

[Stephen Rothwell]

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Hi Avi,

Today's linux-next build (powerpc allyesconfig) produced this warning:

arch/powerpc/kvm/powerpc.c: In function 'kvm_arch_vcpu_ioctl_run':
arch/powerpc/kvm/powerpc.c:278: warning: 'gpr' may be used uninitialized in this function

Yes, I know it is probably a false positive.

Introduced by commit 7f31fad9aad3bb9df95793d72e037bb4d587ee83 ("KVM: PPC:
Use accessor functions for GPR access").
-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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linux-next: kvm tree build warning

[Stephen Rothwell]

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Hi all,

Today's linux-next build (powerpc allyesconfig) produced this warning:

arch/powerpc/kvm/book3s.c: In function '__kvmppc_vcpu_run':
arch/powerpc/kvm/book3s.c:1102: warning: 'ext_bkp.vrsave' may be used uninitialized in this function

Introduced by commit 2609c1d06b6a7952273fb33b33ad32aff0628146 ("KVM: PPC:
Add support for FPU/Altivec/VSX").  This *may* be a false positive but
will be a problem for normal builds where warnings are treated as errors
in arch/powerpc.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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linux-next: kvm tree build warning

[Stephen Rothwell]

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[Not sure what happened to the previous versions To/CC lists, sorry]

Hi all,

Today's linux-next build (powerpc allyesconfig) produced this warning:

arch/powerpc/kvm/book3s.c: In function '__kvmppc_vcpu_run':
arch/powerpc/kvm/book3s.c:1102: warning: 'ext_bkp.vrsave' may be used uninitialized in this function

Introduced by commit 2609c1d06b6a7952273fb33b33ad32aff0628146 ("KVM: PPC:
Add support for FPU/Altivec/VSX").  This *may* be a false positive but
will be a problem for normal builds where warnings are treated as errors
in arch/powerpc.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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Re: linux-next: kvm tree build warning

[Alexander Graf]

On 20.01.2010, at 07:48, Stephen Rothwell wrote:

> [Not sure what happened to the previous versions To/CC lists, sorry]
> 
> Hi all,
> 
> Today's linux-next build (powerpc allyesconfig) produced this warning:
> 
> arch/powerpc/kvm/book3s.c: In function '__kvmppc_vcpu_run':
> arch/powerpc/kvm/book3s.c:1102: warning: 'ext_bkp.vrsave' may be used uninitialized in this function
> 
> Introduced by commit 2609c1d06b6a7952273fb33b33ad32aff0628146 ("KVM: PPC:
> Add support for FPU/Altivec/VSX").  This *may* be a false positive but
> will be a problem for normal builds where warnings are treated as errors
> in arch/powerpc.


This is odd. The same function saves and restores ext_bkp.vrsave under a common condition:

        if (save_vec) {
                if (current->thread.regs->msr & MSR_VEC)
                        giveup_altivec(current);
                memcpy(ext_bkp.vr, current->thread.vr, sizeof(ext_bkp.vr));
                ext_bkp.vscr = current->thread.vscr;
                ext_bkp.vrsave = current->thread.vrsave;
        }


[...]

        if (save_vec && current->thread.used_vr) {
                memcpy(current->thread.vr, ext_bkp.vr, sizeof(ext_bkp.vr));
                current->thread.vscr = ext_bkp.vscr;
                current->thread.vrsave = ext_bkp.vrsave;
        }


So there can't be a case where ext_bkp.vrsave is read, but not written to before, which is what this warning implies, right?
Also, why doesn't gcc complain about vscr too then? They're both used in the very same if statement.

Additionally, while compiling locally I looked for warnings and didn't spot any. So apparently our compiler versions / options don't match. Which version of gcc are you using? I assume a gcc bug.

$ gcc --version
gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]


Alex

Re: linux-next: kvm tree build warning

[Stephen Rothwell]

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Hi Alex,

On Wed, 20 Jan 2010 11:42:28 +0100 Alexander Graf <agraf@suse.de> wrote:
>
> This is odd. The same function saves and restores ext_bkp.vrsave under a common condition:
> 
> So there can't be a case where ext_bkp.vrsave is read, but not written to before, which is what this warning implies, right?

Right.

> Also, why doesn't gcc complain about vscr too then? They're both used in the very same if statement.

I have no idea how gcc makes these decisions. :-(

> Additionally, while compiling locally I looked for warnings and didn't spot any. So apparently our compiler versions / options don't match. Which version of gcc are you using? I assume a gcc bug.
> 
> $ gcc --version
> gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]

I use a 4.4.0 cross compiler (I should update it).
-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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