Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d posted-interrupts

From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d posted-interrupts
Date	2015-11-24 15:40 +0100
Message-ID	<qymVc-Ro-33@gated-at.bofh.it> (permalink)
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On 24/11/2015 15:35, Radim Krcmár wrote:
> > Thanks for your guys' review. Yes, we can introduce a module option
> > for it. According to Radim's comments above, we need use the
> > same policy for PI and non-PI lowest-priority interrupts, so here is the
> > question: for vector hashing, it is easy to apply it for both non-PI and PI
> > case, however, for Round-Robin, in non-PI case, the round robin counter
> > is used and updated when the interrupt is injected to guest, but for
> > PI case, the interrupt is injected to guest totally by hardware, software
> > cannot control it while interrupt delivery, we can only decide the
> > destination vCPU for the PI interrupt in the initial configuration
> > time (guest update vMSI -> QEMU -> KVM). Do you guys have any good
> > suggestion to do round robin for PI lowest-priority? Seems Round robin
> > is not a good way for PI lowest-priority interrupts. Any comments
> > are appreciated!
>
> It's meaningless to try dynamic algorithms with PI so if we allow both
> lowest priority algorithms, I'd let PI handle any lowest priority only
> with vector hashing.  (It's an ugly compromise.)

For now, I would just keep the 4.4 behavior, i.e. disable PI unless
there is a single destination || vector hashing is enabled.  We can flip
the switch later.

Paolo
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Thread

Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-11-16 20:10 +0100
  Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Paolo Bonzini <pbonzini@redhat.com> - 2015-11-17 10:50 +0100
    RE: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-11-24 02:30 +0100
      Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krcmár <rkrcmar@redhat.com> - 2015-11-24 15:40 +0100
        Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Paolo Bonzini <pbonzini@redhat.com> - 2015-11-24 15:40 +0100
          RE: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-11-25 03:00 +0100
            Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Paolo Bonzini <pbonzini@redhat.com> - 2015-11-25 12:40 +0100
  RE: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-11-24 02:30 +0100
    Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-11-24 15:40 +0100
      Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-11-24 15:50 +0100
      RE: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-11-25 04:30 +0100
        Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krcmár <rkrcmar@redhat.com> - 2015-11-25 15:20 +0100
          Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Paolo Bonzini <pbonzini@redhat.com> - 2015-11-25 15:40 +0100
            Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krčmář <rkrcmar@redhat.com> - 2015-11-25 16:50 +0100
              RE: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts "Wu, Feng" <feng.wu@intel.com> - 2015-11-26 07:30 +0100
                Re: [PATCH] KVM: x86: Add lowest-priority support for vt-d  posted-interrupts Radim Krcmár <rkrcmar@redhat.com> - 2015-11-26 15:10 +0100

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