Hi Marc,
On 2019/12/13 19:28, Marc Zyngier wrote:
Hi Zenghui,
On 2019-12-13 10:53, Zenghui Yu wrote:
Hi Eric,
On 2019/12/13 17:42, Eric Auger wrote:
Saving/restoring an unmapped collection is a valid scenario. For
example this happens if a MAPTI command was sent, featuring an
unmapped collection. At the moment the CTE fails to be restored.
Only compare against the number of online vcpus if the rdist
base is set.
Have you actually seen a problem and this patch fixed it? To be honest,
I'm surprised to find that we can map a LPI to an unmapped collection ;)
(and prevent it to be delivered to vcpu with an INT_UNMAPPED_INTERRUPT
error, until someone had actually mapped the collection).
After a quick glance of spec (MAPTI), just as you said, this is valid.
Yes, this is one of the (many) odd bits in the architecture. And there is
a bizarre wording in the MAPC description when V=0:
"Behavior is unpredictable if there are interrupts that are mapped to the
specified collection, with the restriction that further translation
requests
from that device are ignored."
It is really odd that:
- it is unpredictable to unmap the collection with mapped interrupts,
but mapping interrupts to an unmapped collection is fine
Yes, looks odd... Without Eric's patch, I won't even notice it.
I guess that unmapping the collection with mapped interrupts will make
it difficult for Hardware to manage those interrupts' internal states,
but only a guess.
- the notion of "interrupts from that device" doesn't match any of the
MAPC parameters
Looks like a writing mistake, a better statement *might be*
"further translation requests targeting that ICID are ignored"?
Do you hate the GIC already? ;-)
Not yet! (I'd like to continue being messed with GIC and see when I
will hate it :)
If Marc has no objection to this fix, please add
Reviewed-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Thanks for that, I've applied it to the patch and will push out
the update as soon as ra.kernel.org is reachable again.
Thanks,
Zenghui
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