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Re: [Xen-devel] [PATCH v2 10/27] ARM: GICv3: forward pending LPIs to guests





On 03/04/17 15:18, Andre Przywara wrote:
Hi,

Hi Andre,

On 24/03/17 12:03, Julien Grall wrote:
+    /* We may have mapped more host LPIs than the guest actually
asked for. */

Another way, is the interrupt has been received at the same time the
guest is configuring it. What will happen if the interrupt is lost?

I don't see how this would be our problem. If the guest is still about
to configure an LPI, then any incoming one is pretty clearly a spurious
interrupt.
I take it that you mean "mapping an LPI using ITS commands" when you say
"configuring" here. If this is not what you mean, please correct me.

I'd expect a guest to first map the LPI, then enable it and send an INV
command. Doing that differently will not result in any sane behavior (as
in: a guest cannot expect an LPI to come through), so nothing we need to
worry about (from a lost IRQ perspective).

Or what do I miss here?

All host LPIs will be enabled when a device is assigned to a guest. So technically an LPI can come at anytime before the guest is configuring the virtual mapping.

Cheers,

--
Julien Grall

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