Re: [PATCH v2 2/2] util/vfio-helpers: Rework the IOVA allocator to avoid IOVA reserved regions

[Stefan Hajnoczi]

On Tue, Sep 29, 2020 at 10:55:50AM +0200, Eric Auger wrote:
> diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> index ba0ee6e21c..71145970f3 100644
> --- a/util/vfio-helpers.c
> +++ b/util/vfio-helpers.c
> @@ -667,6 +667,50 @@ static bool qemu_vfio_verify_mappings(QEMUVFIOState *s)
>      return true;
>  }
>  
> +static int
> +qemu_vfio_find_fixed_iova(QEMUVFIOState *s, size_t size, uint64_t *iova)
> +{
> +    int i;
> +
> +    for (i = 0; i < s->nb_iova_ranges; i++) {
> +        if (s->usable_iova_ranges[i].end < s->low_water_mark) {
> +            continue;
> +        }
> +        s->low_water_mark =
> +            MAX(s->low_water_mark, s->usable_iova_ranges[i].start);
> +
> +        if (s->usable_iova_ranges[i].end - s->low_water_mark + 1 >= size ||
> +            s->usable_iova_ranges[i].end - s->low_water_mark + 1 == 0) {

I don't understand the == 0 case. It seems like we are allocating an
IOVA beyond usable_iova_ranges[i].end?

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