From: Paul Burton Date: Mon, 5 Sep 2016 15:24:54 +0100 Subject: [PATCH] MIPS: c-r4k: Fix size calc when avoiding IPIs for small icache flushes Commit f70ddc07b637 ("MIPS: c-r4k: Avoid small flush_icache_range SMP calls") adds checks to force use of hit-type cache ops for small icache flushes where they are globalised & index-type cache ops aren't, in order to avoid the overhead of IPIs in those cases. However it calculated the size of the region being flushed incorrectly, subtracting the end address from the start address rather than the reverse. This would have led to an overflow with size wrapping round to some large value, and likely to the special case for avoiding IPIs not actually being hit. Signed-off-by: Paul Burton Cc: James Hogan Fixes: f70ddc07b637 ("MIPS: c-r4k: Avoid small flush_icache_range SMP calls") Reviewed-by: James Hogan Reviewed-by: Florian Fainelli Cc: Huacai Chen Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/14211/ Signed-off-by: Ralf Baechle --- --- a/arch/mips/mm/c-r4k.c +++ b/arch/mips/mm/c-r4k.c @@ -781,7 +781,7 @@ static void r4k_flush_icache_range(unsig * If address-based cache ops are globalized, then we may be * able to avoid the IPI for small flushes. */ - size = start - end; + size = end - start; cache_size = icache_size; if (!cpu_has_ic_fills_f_dc) { size *= 2;