Re: [Qemu-devel] [PATCH] ioapic: kvm: Skip route updates for masked pins

[Jan Kiszka <jan.kiszka@siemens.com>]

On 02.06.19 14:10, Peter Xu wrote:
> On Sun, Jun 02, 2019 at 01:42:13PM +0200, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> Masked entries will not generate interrupt messages, thus do no need to
>> be routed by KVM. This is a cosmetic cleanup, just avoiding warnings of
>> the kind
>>
>> qemu-system-x86_64: vtd_irte_get: detected non-present IRTE (index=0, high=0xff00, low=0x100)
>>
>> if the masked entry happens to reference a non-present IRTE.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> 
> Reviewed-by: Peter Xu <peterx@redhat.com>
> 
> Thanks, Jan.
> 
> The "non-cosmetic" part of clearing of those entries (e.g. including
> when the entries were not setup correctly rather than masked) was
> never really implemented and that task has been on my todo list for
> quite a while but with a very low priority (low enough to sink...).  I
> hope I didn't overlook its importance since AFAICT general OSs should
> hardly trigger those paths and so far I don't see it a very big issue.

I triggered the message during the handover phase from Linux to Jailhouse. That 
involves reprogramming both IOAPIC and IRTEs - likely unusual sequences, I just 
didn't find invalid ones.

Thanks,
Jan

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