Re: [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct

[Fengguang Wu]

Hi Christian and Nikita,

On Mon, Sep 03, 2018 at 06:03:49PM +0200, Christian Borntraeger wrote:
> On 09/03/2018 04:10 PM, Nikita Leshenko wrote:
> > On September 2, 2018 5:21:15 AM, fengguang.wu@xxxxxxxxx wrote:
> > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > > index 8b47507faab5..0c483720de8d 100644
> > > --- a/virt/kvm/kvm_main.c
> > > +++ b/virt/kvm/kvm_main.c
> > > @@ -3892,6 +3892,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
> > >  	if (type == KVM_EVENT_CREATE_VM) {
> > >  		add_uevent_var(env, "EVENT=create");
> > >  		kvm->userspace_pid = task_pid_nr(current);
> > > +		current->kvm = kvm;
> >
> > Is it OK to store `kvm` on the task_struct? What if the thread that
> > originally created the VM exits? From the documentation it seems
> > like a VM is associated with an address space and not a specific
> > thread, so maybe it should be stored on mm_struct?
>
> Yes, ioctls accessing the kvm can happen from all threads.

Good point, thank you for the tips! I'll move kvm pointer to mm_struct.

> > From Documentation/virtual/kvm/api.txt:
> >    Only run VM ioctls from the same process (address space) that was used
> >    to create the VM.
> >
> > -Nikita

Regards,
Fengguang