Re: [Xen-devel] irq_guest_eoi_timer interaction with MSI

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 24/11/08 16:34, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> Perhaps the other way around: Make PHYSDEVOP_eoi imply an unmask,
> as that's what is always happening (whereas not every unmask also wants
> an EOI to be signaled). Below is a draft (compile-tested only) patch that,
> before coding the guest side, I'd appreciate to get comments on -
> especially if it appears reasonable to be done that way, if it meets your
> naming and coding preferences (I'm pretty sure it won't), and of course
> whether it's obviously broken in some respect.

I don't care which way round you do it (PHYSDEVOP_eoi implies unmask, or
vice versa) although you had just about convinced me that you should do it
the other way round to how you've chosen. I don't really mind either way
though.

The fixmap stuff is a bit ugly and I would just have done a
map_domain_page_global() for 32-bit Xen (good enough as far as I'm
concerned). I'm not dead set against your approach if you like it very much,
though.

Setting the need-a-hypercall bit looks racey. Don't you need to set the bit,
then check the guest didn't unmask meanwhile?

 -- Keir



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