> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: Monday, May 23, 2016 5:08 PM > To: Wu, Feng <feng...@intel.com> > Cc: andrew.coop...@citrix.com; dario.faggi...@citrix.com; > george.dun...@eu.citrix.com; Tian, Kevin <kevin.t...@intel.com>; xen- > de...@lists.xen.org; konrad.w...@oracle.com; k...@xen.org > Subject: RE: [PATCH 3/3] VMX: Remove the vcpu from the per-cpu blocking list > after domain termination > > >>> On 23.05.16 at 07:48, <feng...@intel.com> wrote: > >> From: Tian, Kevin > >> Sent: Monday, May 23, 2016 1:19 PM > >> > From: Wu, Feng > >> > Sent: Friday, May 20, 2016 4:54 PM > >> > --- 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!:) > > Well, either there is a possible race (then moving the addition > later just reduces the chances, but doesn't eliminate it), or there > isn't (in which case Kevin's suggestion should probably be followed).
Yes, I agree, adding the cleanup code in domain destroy other than vcpu destroy point just reduces the risk, but not eliminate. So far I don't get a perfect solution to solve this possible race condition. Thanks, Feng > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
