Re: [RFC PATCH-for-7.0] hw/i386/amd_iommu: Fix maybe-uninitialized error with GCC 12

[Paolo Bonzini]

On 3/18/22 15:03, Philippe Mathieu-Daudé wrote:
> +qemu-trivial@

Laurent,

please do not merge this patch as I've sent a replacement and I'll take 
care of merging it.

Paolo

> On 18/3/22 01:41, Philippe Mathieu-Daudé wrote:
> > From: Philippe Mathieu-Daudé <f4bug@amsat.org>
> >
> > Initialize 'oldlevel' early to avoid on Debian/sid:
> >
> >    FAILED: libqemu-x86_64-softmmu.fa.p/hw_i386_amd_iommu.c.o
> >    In function 'pte_get_page_mask',
> >        inlined from 'amdvi_page_walk' at hw/i386/amd_iommu.c:945:25,
> >        inlined from 'amdvi_do_translate' at hw/i386/amd_iommu.c:989:5,
> >        inlined from 'amdvi_translate' at hw/i386/amd_iommu.c:1038:5:
> >    hw/i386/amd_iommu.c:877:38: error: 'oldlevel' may be used 
> > uninitialized [-Werror=maybe-uninitialized]
> >      877 |     return ~((1UL << ((oldlevel * 9) + 3)) - 1);
> >          |                      ~~~~~~~~~~~~~~~~^~~~
> >    hw/i386/amd_iommu.c: In function 'amdvi_translate':
> >    hw/i386/amd_iommu.c:906:41: note: 'oldlevel' was declared here
> >      906 |     unsigned level, present, pte_perms, oldlevel;
> >          |                                         ^~~~~~~~
> >    cc1: all warnings being treated as errors
> >
> > Having:
> >
> >    $ gcc --version
> >    gcc (Debian 12-20220313-1) 12.0.1 20220314 (experimental)
> >
> > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> > ---
> >   hw/i386/amd_iommu.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
> > index 4d13d8e697..b6d299f964 100644
> > --- a/hw/i386/amd_iommu.c
> > +++ b/hw/i386/amd_iommu.c
> > @@ -904,6 +904,7 @@ static void amdvi_page_walk(AMDVIAddressSpace *as, 
> > uint64_t *dte,
> >       /* make sure the DTE has TV = 1 */
> >       if (pte & AMDVI_DEV_TRANSLATION_VALID) {
> >           level = get_pte_translation_mode(pte);
> > +        oldlevel = level;
> >           if (level >= 7) {
> >               trace_amdvi_mode_invalid(level, addr);
> >               return;