Messages in this thread | | | Date | Wed, 06 Aug 2014 16:08:38 +0200 | From | Paolo Bonzini <> | Subject | Re: [PATCH] KVM: x86: always exit on EOIs for interrupts listed in the IOAPIC redir table |
| |
Il 06/08/2014 16:03, Zhang, Yang Z ha scritto: > Paolo Bonzini wrote on 2014-07-31: >> Probably, the guest is masking the interrupt in the redirection table in >> the interrupt routine, i.e. while the interrupt is set in a LAPIC's ISR. >> The simplest fix is to ignore the masking state, we would rather have >> an unnecessary exit rather than a missed IRQ ACK and anyway IOAPIC >> interrupts are not as performance-sensitive as for example MSIs. > > I feel this fixing may hurt performance in some cases. If the mask > bit is set, this means the vector in this entry may be used by other > devices(like a assigned device). But here you set it in eoi exit bitmap > and this will cause vmexit on each EOI which should not happen.
Note that this *was* reported on an assigned device.
IOAPIC should not be a performance-sensitive path. High-performance assigned devices should be using MSIs.
Paolo
| |