Re: [Xen-devel] [PATCH V4 6/8] iommu/arm: Add lightweight iommu_fwspec support

[Oleksandr <olekstysh@xxxxxxxxx>]

On 17.09.19 09:12, Jan Beulich wrote:

Hi, Jan

> On 16.09.2019 20:08, Oleksandr wrote:
> > On 16.09.19 13:40, Jan Beulich wrote:
> > > > +/* per-device IOMMU instance data */
> > > > +struct iommu_fwspec {
> > > > +    /* this device's IOMMU */
> > > > +    struct device *iommu_dev;
> > > > +    /* IOMMU driver private data for this device */
> > > > +    void *iommu_priv;
> > > > +    /* number of associated device IDs */
> > > > +    unsigned int num_ids;
> > > > +    /* IDs which this device may present to the IOMMU */
> > > > +    uint32_t ids[1];
> > > > +};
> > > Note that you abuse xrealloc_flex_struct() when using it with such
> > > a type: The last field is _not_ a flexible array member. Compilers
> > > might legitimately warn if they can prove that you access
> > > p->ids[1] anywhere, despite you (presumably) having allocated enough
> > > space. (I haven't been able to think of a way for the macro to
> > > actually detect and hence refuse such wrong uses.)
> > Indeed, you are right. I am in doubt, whether to retain ported from
> > Linux code (ids[1])
> >
> > and mention about such abuse or change it to deal with real flexible
> > array member (ids[]). Any thoughts?
> I'm of the strong opinion that you should switch to [] (or at
> least [0]) notation.
I got it. Well, will switch to ids[] if there are no objections.

Thank you.

--
Regards,

Oleksandr Tyshchenko


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