Re: [Xen-devel] [RFC PATCH v2 12/22] xen/arm: its: Update irq descriptor for LPIs support

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 30/03/15 15:32, Vijay Kilari wrote:
 >    Stefano suggested to use arch_irq_desc to hold virq and its_device
structure.
> Another question is why another structure irq_guest is created?. Can't we 
> reuse
> arch_irq_desc?

Here is the answer I gave to Stefano when I introduced this new structure:

"I though about it. If we add another field in arch_irq_desc, we will
likely use more memory than xmalloc. This is because most of the
platform doesn't use 1024 interrupts but about 256 interrupts.

As the new field will be a pointer (on ARM64, 8 bytes), that would make
Xen use statically about 8K more.

We could allocate irq_desc dynamically during Xen boot."

This assumption was with only 1 pointer added. As you add 2 pointer, it
will add 16k which is mean increase 15% the current size of the final
Xen binary.

> Is this patch merged?.

Not yet. I sent a v4 2 weeks ago and I expect this patch to be merge as
soon as Ian has time to review it.

Regards,

-- 
Julien Grall

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