Messages in this thread | | | Subject | Re: [PATCH] KVM: arm/arm64: vgic-its: Fix restoration of unmapped collections | From | Zenghui Yu <> | Date | Fri, 13 Dec 2019 22:22:46 +0800 |
| |
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@huawei.com> > > 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
| |