On Wed, 20 Jul 2022 at 12:30, Dr. David Alan Gilbert (git)
<[email protected]> wrote:
>
> From: Hyman Huang(黄勇) <[email protected]>
>
> Setup a negative feedback system when vCPU thread
> handling KVM_EXIT_DIRTY_RING_FULL exit by introducing
> throttle_us_per_full field in struct CPUState. Sleep
> throttle_us_per_full microseconds to throttle vCPU
> if dirtylimit is in service.
>
> Signed-off-by: Hyman Huang(黄勇) <[email protected]>
> Reviewed-by: Peter Xu <[email protected]>
> Message-Id:
> <977e808e03a1cef5151cae75984658b6821be618.1656177590.git.huang...@chinatelecom.cn>
> Signed-off-by: Dr. David Alan Gilbert <[email protected]>
Hi; Coverity points out a problem with this code (CID 1490787):
> +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;
Because dirty_ring_size and TARGET_PAGE_SIZE are both 32 bits,
this multiplication will be done as a 32-bit operation,
which could overflow. You should cast one of the operands
to uint64_t to ensure that the operation is done as a 64 bit
multiplication.
Side note: typo in the variable name: should be 'memory'.
> + if (max_dirtyrate < dirtyrate) {
> + max_dirtyrate = dirtyrate;
> + }
> +
> + return dirty_ring_size_meory_MB * 1000000 / max_dirtyrate;
> +}
thanks
-- PMM
