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hw/i386/amd_iommu: Fix maybe-uninitialized error with GCC 12

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Be more explicit that the loop must roll at least once.  Avoids the
following warning:

  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)

Reported-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2022-03-21 15:30:18 +01:00
parent 3ec5ad4008
commit 17e6ffa6a5
1 changed files with 2 additions and 5 deletions
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7
hw/i386/amd_iommu.c
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@ -913,7 +913,7 @@ static void amdvi_page_walk(AMDVIAddressSpace *as, uint64_t *dte,
}
/* we are at the leaf page table or page table encodes a huge page */
while (level > 0) {
do {
pte_perms = amdvi_get_perms(pte);
present = pte & 1;
if (!present || perms != (perms & pte_perms)) {
@ -932,10 +932,7 @@ static void amdvi_page_walk(AMDVIAddressSpace *as, uint64_t *dte,
}
oldlevel = level;
level = get_pte_translation_mode(pte);
if (level == 0x7) {
break;
}
}
} while (level > 0 && level < 7);
if (level == 0x7) {
page_mask = pte_override_page_mask(pte);