Re: [Xen-devel] [PATCH v5 11/30] ARM: GICv3 ITS: introduce device mapping

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 06/04/17 00:41, Stefano Stabellini wrote:
> > +    /* An Interrupt Translation Table needs to be 256-byte aligned. */
> > +    itt_addr = _xzalloc(nr_events * hw_its->itte_size, 256);
> > +    if ( !itt_addr )
> > +        goto out_unlock;
> > +
> > +    dev = xzalloc(struct its_devices);
> > +    if ( !dev )
> > +        goto out_unlock;
> > +
> > +    /*
> > +     * Allocate the pending_irqs for each virtual LPI. They will be put
> > +     * into the domain's radix tree upon the guest's MAPTI command.
> > +     */
> Please expand the comment with a link to the xen-devel conversation
> about allocation strategy and a TODO saying that we shouldn't need to
> preallocate all pending_irq struct, but we do it for simplicity at the
> moment.
It would have been useful to provide a link of the conversation you 
mention to allow us answering properly rather than loosing a day for 
confirmation. Anyway, I guess you are speaking about [1].
I agree that we would need to take into account the memory to the guest, 
but this is a work beyond GICv3 ITS support as it is not
supported by Xen today.

Even if you do memory accounting, this would have to be reserved in 
advance to avoid failure afterwards. Which is very similar to memory 
allocation...
So can you explain what you would do here?

Cheers,

[1] 
https://lists.xenproject.org/archives/html/xen-devel/2017-03/msg03758.html
--
Julien Grall

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