Thanks,
this looks pretty good to me. A few comments below:
On Fri, Jun 17, 2022 at 10:47:41AM -0400, Tianyu Lan wrote:
> +/**
> + * struct io_tlb_area - IO TLB memory area descriptor
> + *
> + * This is a single area with a single lock.
> + *
> + * @used: The number of used IO TLB block.
> + * @index: The slot index to start searching in this area for next round.
> + * @lock: The lock to protect the above data structures in the map and
> + * unmap calls.
> + */
> +struct io_tlb_area {
> + unsigned long used;
> + unsigned int index;
> + spinlock_t lock;
> +};
This can go into swiotlb.c.
> +void __init swiotlb_adjust_nareas(unsigned int nareas);
And this should be marked static.
> +#define DEFAULT_NUM_AREAS 1
I'd drop this define, the magic 1 and a > 1 comparism seems to
convey how it is used much better as the checks aren't about default
or not, but about larger than one.
I also think that we want some good way to size the default, e.g.
by number of CPUs or memory size.
> +void __init swiotlb_adjust_nareas(unsigned int nareas)
> +{
> + if (!is_power_of_2(nareas)) {
> + pr_err("swiotlb: Invalid areas parameter %d.\n", nareas);
> + return;
> + }
> +
> + default_nareas = nareas;
> +
> + pr_info("area num %d.\n", nareas);
> + /* Round up number of slabs to the next power of 2.
> + * The last area is going be smaller than the rest if
> + * default_nslabs is not power of two.
> + */
Please follow the normal kernel comment style with a /* on its own line.
