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SubjectRe: Questions on the task isolation patches
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On 12/20/2016 4:27 AM, Paolo Bonzini wrote:
> On 16/12/2016 22:00, Chris Metcalf wrote:
>> Sorry, I think I wasn't clear. Normally when you are running task
>> isolated and you enter the kernel, you will get a fatal signal. The
>> exception is if you call prctl itself (or exit), the kernel tolerates
>> it without a signal, since obviously that's how you need to cleanly
>> tell the kernel you are done with task isolation.
> Running in a guest is pretty much the same as running in userspace.
> Would it be possible to exclude the KVM_RUN ioctl as well? QEMU would
> still have to run prctl when a CPU goes to sleep, and KVM_RUN would have
> to enable/disable isolated mode when a VM executes HLT (which should
> never happen anyway in NFV scenarios).

I think that probably makes sense. The flow would be that qemu executes
first the prctl() for task isolation, then the KVM_RUN ioctl. We obviously can't
do it in the other order, so we'd need to make task isolation tolerate KVM_RUN.

I won't try to do it for my next patch series (based on 4.10) though, since I'd
like to get the basic support upstreamed before trying to extend it.

--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com

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