Thanks a lot Marcelo! On Wed, Jan 8, 2014 at 6:25 PM, Marcelo Tosatti <mtosa...@redhat.com> wrote: > On Wed, Jan 08, 2014 at 06:14:15PM -0500, Hu Yaohui wrote: >> Hi guys, >> I think you should be pretty familiar with lapic. I would really >> appreciate it if someone could shed some lights on my problem >> regarding Guest TLB flush IPI. >> Supposed we get two vcpus 0 and 1. >> When vcpu#0 wants to invalidate the tlb entry on vcpu#1. An IPI will >> be generated by lapic on vcpu#0 by writing to ICR which will cause a >> vmexit. >> apic_send_ipi->kvm_irq_delivery_to_apic->kvm_apic_set_irq->__apic_accept_irq >> In __apic_accept_irq, it will call kvm_make_request, kvm_vcpu_kick. >> If vcpu#1 in guest mode, how can it receives this IPI immediately, or >> the stale tlb entry could be accessed. Thanks for your time! > I am using kvm-kmod-3.2 > Two possibilities: > > 2) Hardware does not support APIC virtualization: kvm_vcpu_kick sends an > host-IPI to the remote vcpu, and if that vcpu is in guest mode, a VM-exit > (exit reason: external interrupt) will be triggered due to the host-IPI. > Then on VM-entry (inject_pending_event) the guest-IPI is injected. > if vcpu#1 is not on the same pcpu as the vcpu#0, a host-IPI will be sent. But if they are on the same pcpu, if vcpu#1 is in guest mode. Then the guest tlb flush IPI will wait until the next vcpu#1 vmexit. If that's the case. they are some time that the tlb entry has been invalidated in vcpu#0, but the corresponding entry in vcpu#1 could still been accessed, which seems cause some problem.
> 2) Host CPU supports APIC virtualization (see commit 83d4c286931c and > Intel's documentation): > A bit is set in the posted interrupt section, and a special host-IPI is > delivered to the target cpu where the guest vcpu is scheduled > (vmx_deliver_posted_interrupt) which causes the hardware to > inject the vector (without VM-exit). > > I did not find this function (vmx_deliver_posted_interrupt) in my kvm kernel module. Does that mean my hardware doesn't support APIC virtualization? Thanks for your time! Best Wishes, Yaohui Hu -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
