Hi Macelo, I am sorry to bother you again. In your first possibility, kvm_vcpu_kick sends an host-IPI to the remote vcpu, and if that vcpu is in guest mode, a VM-exit will be triggered due to the host-IPI. My question is if the vcpu has accessed the stale tlb entry before the host-IPI arrives, what will happen? Thanks for your time! Best Wishes, Yaohui Hu On Wed, Jan 8, 2014 at 6:35 PM, Hu Yaohui <loki2441@xxxxxxxxx> wrote: > Thanks a lot Marcelo! > > On Wed, Jan 8, 2014 at 6:25 PM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
