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    Subject[PATCH v5 7/9] net/ice: fix initializing the bitmap in the switch code
    Date
    Kbuild spotted the following bug during the testing of one of
    the optimizations:

    In file included from include/linux/cpumask.h:12,
    [...]
    from drivers/net/ethernet/intel/ice/ice_switch.c:4:
    drivers/net/ethernet/intel/ice/ice_switch.c: In function 'ice_find_free_recp_res_idx.constprop':
    include/linux/bitmap.h:447:22: warning: 'possible_idx[0]' is used uninitialized [-Wuninitialized]
    447 | *map |= GENMASK(start + nbits - 1, start);
    | ^~
    In file included from drivers/net/ethernet/intel/ice/ice.h:7,
    from drivers/net/ethernet/intel/ice/ice_lib.h:7,
    from drivers/net/ethernet/intel/ice/ice_switch.c:4:
    drivers/net/ethernet/intel/ice/ice_switch.c:4929:24: note: 'possible_idx[0]' was declared here
    4929 | DECLARE_BITMAP(possible_idx, ICE_MAX_FV_WORDS);
    | ^~~~~~~~~~~~
    include/linux/types.h:11:23: note: in definition of macro 'DECLARE_BITMAP'
    11 | unsigned long name[BITS_TO_LONGS(bits)]
    | ^~~~

    %ICE_MAX_FV_WORDS is 48, so bitmap_set() here was initializing only
    48 bits, leaving a junk in the rest 16.
    It was previously hidden due to that filling 48 bits makes
    bitmap_set() call external __bitmap_set(), but after making it use
    plain bit arithmetics on small bitmaps, compilers started seeing
    the issue. It was still working because those 16 weren't used
    anywhere anyhow.
    bitmap_{clear,set}() are not really intended to initialize bitmaps,
    rather to modify already initialized ones, as they don't do anything
    past the passed number of bits. The correct function to do this in
    that particular case is bitmap_fill(), so use it here. It will do
    `*possible_idx = ~0UL` instead of `*possible_idx |= GENMASK(47, 0)`,
    not leaving anything in an undefined state.

    Fixes: fd2a6b71e300 ("ice: create advanced switch recipe")
    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
    ---
    drivers/net/ethernet/intel/ice/ice_switch.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/net/ethernet/intel/ice/ice_switch.c b/drivers/net/ethernet/intel/ice/ice_switch.c
    index 8d8f3eec79ee..9b2872e89151 100644
    --- a/drivers/net/ethernet/intel/ice/ice_switch.c
    +++ b/drivers/net/ethernet/intel/ice/ice_switch.c
    @@ -4934,7 +4934,7 @@ ice_find_free_recp_res_idx(struct ice_hw *hw, const unsigned long *profiles,
    bitmap_zero(recipes, ICE_MAX_NUM_RECIPES);
    bitmap_zero(used_idx, ICE_MAX_FV_WORDS);

    - bitmap_set(possible_idx, 0, ICE_MAX_FV_WORDS);
    + bitmap_fill(possible_idx, ICE_MAX_FV_WORDS);

    /* For each profile we are going to associate the recipe with, add the
    * recipes that are associated with that profile. This will give us
    --
    2.36.1
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