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    SubjectRe: [PATCH 1/4] vdpa: introduce config op to get valid iova range
    On Thu, Aug 06, 2020 at 08:29:22AM -0400, Michael S. Tsirkin wrote:
    > On Thu, Aug 06, 2020 at 03:03:55PM +0300, Eli Cohen wrote:
    > > On Wed, Aug 05, 2020 at 08:51:56AM -0400, Michael S. Tsirkin wrote:
    > > > On Wed, Jun 17, 2020 at 11:29:44AM +0800, Jason Wang wrote:
    > > > > This patch introduce a config op to get valid iova range from the vDPA
    > > > > device.
    > > > >
    > > > > Signed-off-by: Jason Wang <jasowang@redhat.com>
    > > > > ---
    > > > > include/linux/vdpa.h | 14 ++++++++++++++
    > > > > 1 file changed, 14 insertions(+)
    > > > >
    > > > > diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
    > > > > index 239db794357c..b7633ed2500c 100644
    > > > > --- a/include/linux/vdpa.h
    > > > > +++ b/include/linux/vdpa.h
    > > > > @@ -41,6 +41,16 @@ struct vdpa_device {
    > > > > unsigned int index;
    > > > > };
    > > > >
    > > > > +/**
    > > > > + * vDPA IOVA range - the IOVA range support by the device
    > > > > + * @start: start of the IOVA range
    > > > > + * @end: end of the IOVA range
    > > > > + */
    > > > > +struct vdpa_iova_range {
    > > > > + u64 start;
    > > > > + u64 end;
    > > > > +};
    > > > > +
    > > >
    > > >
    > > > This is ambiguous. Is end in the range or just behind it?
    > > > How about first/last?
    > >
    > > It is customary in the kernel to use start-end where end corresponds to
    > > the byte following the last in the range. See struct vm_area_struct
    > > vm_start and vm_end fields
    >
    > Exactly my point:
    >
    > include/linux/mm_types.h: unsigned long vm_end; /* The first byte after our end address
    >
    > in this case Jason wants it to be the last byte, not one behind.
    >
    >
    Maybe start, size? Not ambiguous, and you don't need to do annoying
    calculations like size = last - start + 1

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