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

On Mon, 30 Jan 2012, Avi Kivity wrote:

On 01/30/2012 05:32 PM, Eric B Munson wrote:

quoted

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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.

quoted

) 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.

Okay, I will rebase the per vcpu patches and resend those.

Eric