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Re: [Xen-devel] [PATCH 0/4] Add posted interrupt supporting

Jan Beulich wrote on 2013-04-19:
>>>> On 19.04.13 at 13:49, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> wrote:
>> I am also interested in this question and I cannot find a clear answer:
>> when a guest vcpu wants to issue an IPI to another vcpu, will it trap
>> into Xen? Or will everything work automagically?
> For PV, obviously, this is done by a hypercall.
> For HVM this ought to depend on the level of hardware assistance
> in LAPIC virtualization: Traditionally, the involved LAPIC register
> accesses would trap into the hypervisor. But with full APIC
> virtualization, this should not be happening anymore.
No. Actually, only self IPI will handled by hardware directly. All other vIPIs 
still cause APIC write vmexit.

Best regards,

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