Re: KVM handling external interrupts

[Jan Kiszka <jan.kiszka@web.de>]

[-- Attachment #1: Type: text/plain, Size: 1250 bytes --]

On 2012-06-10 10:41, Abel Gordon wrote:
> Jan Kiszka <jan.kiszka@web.de> wrote on 07/06/2012 18:05:55:
> 
>> It remains a fragile approach:
>>  - host-side reverse translations may not return a stable result, thus
>>    may require to redo this step several times
>>  - the guest may decide to remove/disable the device you chose for
>>    appending the IDT
>>  - changing the real BAR size can confuse the guest, or it only maps
>>    what it requires of the real device
>> That's why I consider it nasty.
> 
> Yep, these are corner cases we should deal with but they are not part
> of the common case/critical path.
> 
>> I'm wondering if redirecting (to different cores) or masking (at
>> device/IOAPIC/LAPIC level) of non-guest interrupts and only relying on
>> preemption timer/NMI isn't simpler. Then you wouldn't have to shadow the
>> IDT.
> 
> Yep, as we suggested in the paper, that could be also an alternative.
> Is it really simpler ? Again, depends who you ask and what you need to
> change.
> All the alternatives have a set of pros and cons.
> 

For sure. But avoiding the shadow IDT would likely mean avoiding
userspace changes for KVM. And that means simplification. And avoid PCI
dependencies.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 262 bytes --]