Re: [Xen-devel] [PATCH 3/3] VMX: Remove the vcpu from the per-cpu blocking list after domain termination

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Tian, Kevin
> Sent: Monday, May 23, 2016 1:19 PM
> To: Wu, Feng <feng.wu@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx
> Cc: keir@xxxxxxx; jbeulich@xxxxxxxx; andrew.cooper3@xxxxxxxxxx;
> george.dunlap@xxxxxxxxxxxxx; dario.faggioli@xxxxxxxxxx;
> konrad.wilk@xxxxxxxxxx
> Subject: RE: [PATCH 3/3] VMX: Remove the vcpu from the per-cpu blocking list
> after domain termination
> 
> > From: Wu, Feng
> > Sent: Friday, May 20, 2016 4:54 PM
> >
> > We need to make sure the bocking vcpu is not in any per-cpu blocking list
> > when the associated domain is going to be destroyed.
> >
> > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> > ---
> >  xen/arch/x86/hvm/vmx/vmx.c | 32
> > ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> >
> > diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> > index 4862b13..e74b3e7 100644
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -248,6 +248,36 @@ void vmx_pi_hooks_deassign(struct domain *d)
> >      d->arch.hvm_domain.vmx.pi_switch_to = NULL;
> >  }
> >
> > +static void vmx_pi_blocking_list_cleanup(struct domain *d)
> 
> Is it more natural to move such cleanup under vcpu destroy?

Yes, indeed it is more natural to add this function when vcpu is destroyed,
however, the reason I add it here is I still have some concerns about the 
timing.
When the VM is destroyed, here is the calling path:

- vmx_pi_hooks_deassign() -->
......
- vmx_vcpu_destroy() --> 
......
- vmx_domain_destroy()
......

As I replied in the previous mail, when we remove the vcpus from the blocking
list, there might be some _in-flight_ call to the hooks, so I put the cleanup
code in the vmx_domain_destroy(), which is a bit more far from 
vmx_pi_hooks_deassign,
and hence safer. If you have any other good ideas, I am all ears!:)

Thanks,
Feng


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