> From: Wu, Feng > Sent: Monday, February 29, 2016 11:00 AM > > This is the core logic handling for VT-d posted-interrupts. Basically it > deals with how and when to update posted-interrupts during the following > scenarios: > - vCPU is preempted > - vCPU is slept > - vCPU is blocked > > When vCPU is preempted/slept, we update the posted-interrupts during > scheduling by introducing two new architecutral scheduler hooks: > vmx_pi_switch_from() and vmx_pi_switch_to(). When vCPU is blocked, we > introduce a new architectural hook: arch_vcpu_block() to update > posted-interrupts descriptor. > > Besides that, before VM-entry, we will make sure the 'NV' filed is set > to 'posted_intr_vector' and the vCPU is not in any blocking lists, which > is needed when vCPU is running in non-root mode. The reason we do this check > is because we change the posted-interrupts descriptor in vcpu_block(), > however, we don't change it back in vcpu_unblock() or when vcpu_block() > directly returns due to event delivery (in fact, we don't need to do it > in the two places, that is why we do it before VM-Entry). > > When we handle the lazy context switch for the following two scenarios: > - Preempted by a tasklet, which uses in an idle context. > - the prev vcpu is in offline and no new available vcpus in run queue. > We don't change the 'SN' bit in posted-interrupt descriptor, this > may incur spurious PI notification events, but since PI notification > event is only sent when 'ON' is clear, and once the PI notificatoin > is sent, ON is set by hardware, hence no more notification events > before 'ON' is clear. Besides that, spurious PI notification events are > going to happen from time to time in Xen hypervisor, such as, when > guests trap to Xen and PI notification event happens, there is > nothing Xen actually needs to do about it, the interrupts will be > delivered to guest atht the next time we do a VMENTRY. > > CC: Keir Fraser <k...@xen.org> > CC: Jan Beulich <jbeul...@suse.com> > CC: Andrew Cooper <andrew.coop...@citrix.com> > CC: Kevin Tian <kevin.t...@intel.com> > CC: George Dunlap <george.dun...@eu.citrix.com> > CC: Dario Faggioli <dario.faggi...@citrix.com> > Suggested-by: Yang Zhang <yang.z.zh...@intel.com> > Suggested-by: Dario Faggioli <dario.faggi...@citrix.com> > Suggested-by: George Dunlap <george.dun...@citrix.com> > Suggested-by: Jan Beulich <jbeul...@suse.com> > Signed-off-by: Feng Wu <feng...@intel.com> > Reviewed-by: George Dunlap <george.dun...@citrix.com>
Acked-by: Kevin Tian <kevin.t...@intel.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
