On Fri, 29 Jul 2022 at 16:17, <huang...@chinatelecom.cn> wrote:
>
> From: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
>
> Coverity points out a overflow problem when computing MB,
> dirty_ring_size and TARGET_PAGE_SIZE are both 32 bits,
> multiplication will be done as a 32-bit operation, which
> could overflow. Simplify the formula.
>
> Meanwhile, fix spelling mistake of variable name.
>
> Reported-by: Peter Maydell <peter.mayd...@linaro.org>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> Signed-off-by: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
> ---
> softmmu/dirtylimit.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
> index 8d98cb7..ab62f29 100644
> --- a/softmmu/dirtylimit.c
> +++ b/softmmu/dirtylimit.c
> @@ -236,14 +236,14 @@ static inline int64_t
> dirtylimit_dirty_ring_full_time(uint64_t dirtyrate)
> {
> static uint64_t max_dirtyrate;
> uint32_t dirty_ring_size = kvm_dirty_ring_size();
> - uint64_t dirty_ring_size_meory_MB =
> - dirty_ring_size * TARGET_PAGE_SIZE >> 20;
> + uint32_t dirty_ring_size_memory_MB =
> + dirty_ring_size >> (20 - TARGET_PAGE_BITS);
>
> if (max_dirtyrate < dirtyrate) {
> max_dirtyrate = dirtyrate;
> }
>
> - return dirty_ring_size_meory_MB * 1000000 / max_dirtyrate;
> + return dirty_ring_size_memory_MB * 1000000 / max_dirtyrate;
Now you've changed dirty_ring_size_memory_MB to 32 bits,
this multiplication is going to be done at 32 bit
precision and can overflow. Adding 'ULL' to the '1000000'
is one way to fix that.
thanks
-- PMM
