[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Interrupt to CPU routing in HVM domains - again
On Fri, Sep 05, 2008 at 11:15:43AM -0400, Steve Ofsthun wrote: > While the event channel delivery code "binds" HVM event channel interrupts > to VCPU0, the interrupt is delivered via the emulated IOAPIC. The guest OS > may program this "hardware" to deliver the interrupt to other VCPUs. For > linux, this gets done by the irqbalance code among others. Xen overrides > this routing for the timer 0 interrupt path in vioapic.c under the #define > IRQ0_SPECIAL_ROUTING. We hacked our version of Xen to piggyback on this > code to force all event channel interrupts for HVM guests to also avoid any > guest rerouting: > > #ifdef IRQ0_SPECIAL_ROUTING > /* Force round-robin to pick VCPU 0 */ > if ( ((irq == hvm_isa_irq_to_gsi(0)) && pit_channel0_enabled()) || > is_hvm_callback_irq(vioapic, irq) ) > deliver_bitmask = (uint32_t)1; > #endif Yes, please - Solaris 10 PV drivers are buggy in that they use the current VCPUs vcpu_info. I just found this bug, and it's getting fixed, but if this makes sense anyway, it'd be good. > This routing override provides a significant performance boost [or rather > avoids the performance penalty] for SMP PV drivers up until the time that > VCPU0 is saturated with interrupts. You can probably achieve the same Of course there's no requirement that the evtchn is actually dealt with on the same CPU, just the callback IRQ and the evtchn "ack" (clearing evtchn_upcall_pending). regards john _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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