Messages in this thread | | | Date | Mon, 22 Sep 2014 17:08:12 -0300 | From | Marcelo Tosatti <> | Subject | Re: [PATCH] kvm: don't take vcpu mutex for obviously invalid vcpu ioctls |
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On Fri, Sep 19, 2014 at 04:03:25PM -0700, David Matlack wrote: > vcpu ioctls can hang the calling thread if issued while a vcpu is > running.
There is a mutex per-vcpu, so thats expected, OK...
> If we know ioctl is going to be rejected as invalid anyway, > we can fail before trying to take the vcpu mutex.
Consider a valid ioctl that takes the vcpu mutex. If you need immediate access for that valid ioctl, it is necessary to interrupt thread which KVM_RUN ioctl executes.
So knowledge of whether KVM_RUN is being executed is expected in userspace (either that or ask the KVM_RUN thread to run the ioctl for you, as qemu does).
Can't see why having different behaviour for valid/invalid ioctls is a good thing.
> This patch does not change functionality, it just makes invalid ioctls > fail faster.
Should not be executing vcpu ioctls without interrupt KVM_RUN in the first place.
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