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

["Philippe Mathieu-Daudé" <philippe.mathieu.daude@gmail.com>]

+qemu-trivial@

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;