Re: [PATCH] hw/vfio/common: Fix a small boundary issue of a trace

[Damien Hedde]

On 4/6/22 10:14, chenxiang via wrote:
> From: Xiang Chen <chenxiang66@hisilicon.com>
>
> Right now the trace of vfio_region_sparse_mmap_entry is as follows:
> vfio_region_sparse_mmap_entry sparse entry 0 [0x1000 - 0x9000]
> Actually the range it wants to show is [0x1000 - 0x8fff]，so fix it.
>
> Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
> ---
>   hw/vfio/common.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 080046e3f5..0b3808caf8 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1546,7 +1546,7 @@ static int vfio_setup_region_sparse_mmaps(VFIORegion 
> *region,
>       for (i = 0, j = 0; i < sparse->nr_areas; i++) {
>           trace_vfio_region_sparse_mmap_entry(i, sparse->areas[i].offset,
>                                               sparse->areas[i].offset +
> -                                            sparse->areas[i].size);
> +                                            sparse->areas[i].size - 1);
>   
>           if (sparse->areas[i].size) {
>               region->mmaps[j].offset = sparse->areas[i].offset;

If the size if zero, the trace will be weird with an underflow if offset 
is zero as well.
Maybe just change the trace by inverting the right bracket ?
eg: [0x1000 - 0x9000[
Or don't trace in that case ? (but I am not maintainer of this, so maybe 
that does not make sense).

--
Damien