Re: [Xen-devel] [PATCH 04/28] ARM: GICv3 ITS: allocate device and collection table

[Julien Grall <julien.grall@xxxxxxx>]

On 23/03/17 18:06, Andre Przywara wrote:
> Hi,
Hi Andre,

> On 06/02/17 17:43, Julien Grall wrote:
> > Hi,
> >
> > On 30/01/17 18:31, Andre Przywara wrote:
> > > +int gicv3_its_init(struct host_its *hw_its)
> > > +{
> > > +    uint64_t reg;
> > > +    int i;
> > > +
> > > +    hw_its->its_base = ioremap_nocache(hw_its->addr, hw_its->size);
> > > +    if ( !hw_its->its_base )
> > > +        return -ENOMEM;
> > > +
> > > +    for ( i = 0; i < GITS_BASER_NR_REGS; i++ )
> > > +    {
> > > +        void __iomem *basereg = hw_its->its_base + GITS_BASER0 + i * 8;
> > > +        int type;
> > > +
> > > +        reg = readq_relaxed(basereg);
> > > +        type = (reg & GITS_BASER_TYPE_MASK) >> GITS_BASER_TYPE_SHIFT;
> > > +        switch ( type )
> > > +        {
> > > +        case GITS_BASER_TYPE_NONE:
> > > +            continue;
> > > +        case GITS_BASER_TYPE_DEVICE:
> > > +            /* TODO: find some better way of limiting the number of
> > > devices */
> > > +            its_map_baser(basereg, reg, BIT(max_its_device_bits));
> > > +            break;
> > > +        case GITS_BASER_TYPE_COLLECTION:
> > > +            its_map_baser(basereg, reg, NR_CPUS);
> > And I forgot to mention about the collection. Same remark as for the
> > device collection, NR_CPUS is the maximum size.
> NR_CPUS is 128, entry size for each collection is probably around 8 or
> 16 bytes, if at all. This gives me half a page, worst case.
> The granularity of the table memory handed to the ITS is (64K|16K|4K),
> so as we only hand over whole pages to the ITS, I don't see how we can
> save memory here.
> Beside, we have other memory issues to worry about than this single 64K
> allocated at boot time.
>
> So if you don't mind, I'd just keep it as it is. I am happy to revisit
> this once NR_CPUS gets significantly increased.
Replacing NR_CPUS by nr_cpu_ids would have addressed my comment and 
requiring less keystrokes than writing this e-mail.
Cheers,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel