Re: [PATCH 3/4 V10] Add ioctl for KVMCLOCK_GUEST_STOPPED

[Avi Kivity]

On 01/30/2012 05:32 PM, Eric B Munson wrote:
> > 
> > Can you point me to the discussion that moved this to be a vm ioctl?  In
> > general vm ioctls that do things for all vcpus are racy, like here. 
> > You're accessing variables that are protected by the vcpu mutex, and not
> > taking the mutex (nor can you, since it is held while the guest is
> > running, unlike most kernel mutexes).
> > 
>
> Jan Kiszka suggested that becuase there isn't a use case for notifying
> individual vcpus (can vcpu's be paused individually?

They can, though the guest will grind to a halt very soon.

> ) that it makes more sense
> to have a vm ioctl.
>
> http://thread.gmane.org/gmane.comp.emulators.qemu/131624
>
> If the per vcpu ioctl is the right choice I can resend those patches.

The races are solvable but I think it's easier in userspace.  It's also
more flexible, though I don't really see a use for this flexibility.

-- 
error compiling committee.c: too many arguments to function

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