Hello Julien,
On 22.11.18 19:22, Julien Grall wrote:
My biggest worry is you are doing optimization on a vGIC that is not
fully compliant with how a GIC should behave (e.g edge vs level) and
with very fragile locking.
Yep, old VGIC locking looks pretty terrible.
If you are interested, Andre can provides more details.
Being honest, I'm not fully understand edge vs level problem there. It
would be good to get better view on it.
I can't comment without any numbers here. Bear in mind that we fixed
bugs in Xen 4.12 (including spectre/meltdown and missing barriers) that
wasn't backported to Xen 4.10. It is entirely possible that it
introduced slowness but it also ensure the code is behaving correctly.
For sure, I know that. It was rather a political decision.
Anyway, if there are performance regression we should investigate them
and discuss how we can address/limit them. Similarly for the new vGIC,
if you think it is too slow, then we need to know why before we get rid
of the old vGIC.
Yep.
There are no guest prioritization at the moment. However, we may want to
introduce it to give priority to one guest over.
But still, processing of IRQs by a hypervisor (e.g. moving them from gic
to vgic for guests IRQs) has a higher priority over any guest execution.
--
Sincerely,
Andrii Anisov.
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