Paolo Bonzini wrote on 2015-07-31: > > > On 31/07/2015 04:49, Steve Rutherford wrote: >> Oh... Yeah. That's a damn good point, given that the interrupt can be >> injected from another thread while one is in that guest vcpu. >> >> Easiest time to update the TMR should be on guest entry through >> vcpu_scan_ioapic, as before. >> >> The best way to go is probably to ditch the new per vcpu EOI exit >> bitmap, and just update/use the TMR. There's no reason to duplicate >> that data in the representation of the apic (I suspect that the >> duplication was inspired by my mistaken notion of the TMR). The >> IOAPIC exit check can use the TMR instead. >> >> Based upon my reading of the SDM, the only reason that the eoi exit >> bitmaps are not the exact same as the TMR is that it is possible to >> have virtual-interrupt delivery enabled /without/ an apic access page >> (Note: V-ID => EOI exit bitmap enabled). >> >> Yang, do you happen to know if that is the case? >> >> [Note: Just looked back at the old code for updating the EOI exit >> bitmaps, which for some reason was configured to trigger EOI exits >> for all IOAPIC interrupts, not just level-triggered IOAPIC >> interrupts. Which is weird, and I believe totally unecessary.] > > The RTC interrupt needs to trigger an EOI exit with the in-kernel > IOAPIC, in order to detect coalesced interrupts. This is necessary to > avoid severe time drift in Windows guest. Correct! EOI exit bitmap is not absolutely same with TMR. Some interrupts (especially timer interrupt) which is edge trigger but need a notification when it got injected into guest. > > Paolo Best regards, Yang -- 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
