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From: "Radim Kr?má?" <rkrcmar@redhat.com>
To: "Wu, Feng" <feng.wu@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"gleb@kernel.org" <gleb@kernel.org>,
	"dwmw2@infradead.org" <dwmw2@infradead.org>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"jiang.liu@linux.intel.com" <jiang.liu@linux.intel.com>,
	"eric.auger@linaro.org" <eric.auger@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI
Date: Wed, 14 Jan 2015 17:59:10 +0100	[thread overview]
Message-ID: <20150114165909.GA1283@potion.brq.redhat.com> (raw)
In-Reply-To: <E959C4978C3B6342920538CF579893F00234E4CD@SHSMSX104.ccr.corp.intel.com>

2015-01-14 01:27+0000, Wu, Feng:
> > the new
> > > hardware even doesn't consider the TPR for lowest priority interrupts
> > delivery.
> > 
> > A bold move ... what hardware was the first to do so?
> 
> I think it was starting with Nehalem.

Thanks,  (Could be that QPI can't inform about TPR changes anymore ...)

I played with Linux's TPR on Haswell and found that is has no effect.

> > > As discussed with Paolo before, I will submit a patch to support lowest
> > priority for PI
> > > after this series is merged.
> > 
> > Sure, I see only two good solutions though
> >  1) don't optimize lowest priority with PI
> >  2) don't balance lowest priority
> 
> As discussed with Paolo before, as the first stage, we only support single-CPU
> lowest priority for PI, since this is a new hardware feature enabling, Paolo trends
> to do simple things in the beginning.

I agree, that is the best we can do without changing lowest priority.

I wanted to avoid a future solution that would introduce two behaviors
for lowest priority (round robin and something).
Round robin (anything dynamic) can't be done with PI, hence the question
if we can remove it.

>                                       Then we will support full lowest priority for
> it, such as, using vector hashing (this is one method of what hardware do for
> lowest priority today), I need to get some detailed information about this from
> hardware guys before enabling it.

I wasn't able to confirm hashing, is it a recent addition?
I'm not sure we want it then:  OS still has to take care of proper
distribution, being predictable is better than uncertain gains, and
we'll save code.

The same should apply to hardware though ... do you know the reasons
behind vector hashing?

Thank you.

  parent reply	other threads:[~2015-01-14 17:00 UTC|newest]

Thread overview: 141+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-12 15:14 [v3 00/26] Add VT-d Posted-Interrupts support Feng Wu
2014-12-12 15:14 ` [v3 01/26] genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a VCPU Feng Wu
2014-12-12 15:14 ` [v3 02/26] iommu: Add new member capability to struct irq_remap_ops Feng Wu
2015-01-28 15:22   ` David Woodhouse
2015-01-29  8:34     ` Wu, Feng
2014-12-12 15:14 ` [v3 03/26] iommu, x86: Define new irte structure for VT-d Posted-Interrupts Feng Wu
2015-01-28 15:26   ` David Woodhouse
2014-12-12 15:14 ` [v3 04/26] iommu, x86: Implement irq_set_vcpu_affinity for intel_ir_chip Feng Wu
2015-01-28 15:26   ` David Woodhouse
2015-01-29  7:55     ` Wu, Feng
2014-12-12 15:14 ` [v3 05/26] x86, irq: Implement irq_set_vcpu_affinity for pci_msi_ir_controller Feng Wu
2014-12-12 15:14 ` [v3 06/26] iommu, x86: No need to migrating irq for VT-d Posted-Interrupts Feng Wu
2014-12-18 14:26   ` Zhang, Yang Z
2014-12-19  1:40     ` Wu, Feng
2014-12-19  1:46       ` Zhang, Yang Z
2014-12-19 11:59         ` Paolo Bonzini
2014-12-23  0:37           ` Zhang, Yang Z
2014-12-23  8:47             ` Paolo Bonzini
2014-12-23  9:07               ` Wu, Feng
2014-12-23  9:34                 ` Paolo Bonzini
2014-12-24  1:38                   ` Zhang, Yang Z
2014-12-24  2:12                     ` Jiang Liu
2014-12-24  2:32                       ` Zhang, Yang Z
2014-12-24  3:08                         ` Wu, Feng
2014-12-24  4:04                           ` Zhang, Yang Z
2014-12-24  4:54                         ` Jiang Liu
2015-01-28 15:29   ` David Woodhouse
2014-12-12 15:14 ` [v3 07/26] iommu, x86: Add cap_pi_support() to detect VT-d PI capability Feng Wu
2015-01-28 15:32   ` David Woodhouse
2014-12-12 15:14 ` [v3 08/26] iommu, x86: Add intel_irq_remapping_capability() for Intel Feng Wu
2015-01-28 15:37   ` David Woodhouse
2015-01-29  8:57     ` Wu, Feng
2014-12-12 15:14 ` [v3 09/26] iommu, x86: define irq_remapping_cap() Feng Wu
2014-12-12 15:14 ` [v3 10/26] KVM: change struct pi_desc for VT-d Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 11/26] KVM: Add some helper functions for Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 12/26] KVM: Initialize VT-d Posted-Interrupts Descriptor Feng Wu
2014-12-18 15:19   ` Zhang, Yang Z
2014-12-12 15:14 ` [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI Feng Wu
2014-12-18 14:49   ` Zhang, Yang Z
2014-12-18 16:58     ` Paolo Bonzini
2014-12-19  1:13       ` Zhang, Yang Z
2014-12-19  1:30         ` Wu, Feng
2014-12-19  1:30       ` Wu, Feng
2014-12-19  1:47         ` Zhang, Yang Z
2014-12-19 11:59         ` Paolo Bonzini
2014-12-19 23:48           ` Wu, Feng
2014-12-20 13:16             ` Paolo Bonzini
2014-12-22  4:48               ` Wu, Feng
2014-12-22  9:27                 ` Paolo Bonzini
2014-12-22 11:04                   ` Wu, Feng
2014-12-22 11:06                     ` Paolo Bonzini
2014-12-22 11:17                       ` Wu, Feng
2014-12-22 11:23                         ` Paolo Bonzini
2014-12-22 14:13                           ` Yong Wang
2015-01-09 14:54   ` Radim Krčmář
2015-01-09 14:56     ` Paolo Bonzini
2015-01-09 15:12       ` Radim Krčmář
2015-01-09 15:18         ` Paolo Bonzini
2015-01-09 15:47           ` Radim Krčmář
2015-01-13  0:27       ` Wu, Feng
2015-01-13 16:17         ` Radim Kr?má?
2015-01-14  1:27           ` Wu, Feng
2015-01-14 13:02             ` Paolo Bonzini
2015-01-14 16:59             ` Radim Kr?má? [this message]
2015-01-20 21:04               ` Nadav Amit
2015-01-21 21:16                 ` Radim Kr?má?
2014-12-12 15:14 ` [v3 14/26] KVM: Get Posted-Interrupts descriptor address from struct kvm_vcpu Feng Wu
2014-12-12 15:14 ` [v3 15/26] KVM: add interfaces to control PI outside vmx Feng Wu
2014-12-12 15:14 ` [v3 16/26] KVM: Make struct kvm_irq_routing_table accessible Feng Wu
2014-12-17 16:17   ` Paolo Bonzini
2014-12-19  2:19     ` Wu, Feng
2014-12-19 11:59       ` Paolo Bonzini
2014-12-19 23:39         ` Wu, Feng
2014-12-12 15:14 ` [v3 17/26] KVM: make kvm_set_msi_irq() public Feng Wu
2014-12-17 17:32   ` Paolo Bonzini
2014-12-12 15:14 ` [v3 18/26] KVM: kvm-vfio: User API for VT-d Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 19/26] KVM: kvm-vfio: implement the VFIO skeleton " Feng Wu
2014-12-12 15:14 ` [v3 20/26] KVM: x86: kvm-vfio: VT-d posted-interrupts setup Feng Wu
2014-12-12 15:14 ` [v3 21/26] x86, irq: Define a global vector for VT-d Posted-Interrupts Feng Wu
2014-12-18 14:54   ` Zhang, Yang Z
2014-12-19  0:52     ` Wu, Feng
2015-01-30 18:18   ` H. Peter Anvin
2015-02-02  1:06     ` Wu, Feng
2015-02-23 22:04   ` Marcelo Tosatti
2014-12-12 15:14 ` [v3 22/26] KVM: Define a wakeup worker thread for vCPU Feng Wu
2014-12-12 15:14 ` [v3 23/26] KVM: Update Posted-Interrupts Descriptor when vCPU is preempted Feng Wu
2014-12-17 17:11   ` Paolo Bonzini
2014-12-18  3:15     ` Wu, Feng
2014-12-18  8:32       ` Paolo Bonzini
2014-12-19  2:09         ` Wu, Feng
2015-02-23 22:21   ` Marcelo Tosatti
2015-03-02  9:12     ` Wu, Feng
2014-12-12 15:14 ` [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked Feng Wu
2014-12-17 17:09   ` Paolo Bonzini
2014-12-18  3:16     ` Wu, Feng
2014-12-18  8:37       ` Paolo Bonzini
2014-12-19  2:51         ` Wu, Feng
2015-02-25 21:50   ` Marcelo Tosatti
2015-02-26  8:08     ` Wu, Feng
2015-02-26 23:41       ` Marcelo Tosatti
2015-02-26 23:40   ` Marcelo Tosatti
2015-03-02 13:36     ` Wu, Feng
2015-03-04 12:06       ` Marcelo Tosatti
2015-03-06  6:51         ` Wu, Feng
2015-03-12  1:15           ` Marcelo Tosatti
2015-03-16 11:42             ` Wu, Feng
2015-03-25 23:17               ` Marcelo Tosatti
2015-03-27  6:34                 ` Wu, Feng
2015-03-27 19:30                   ` Marcelo Tosatti
2015-03-30  4:46                     ` Wu, Feng
2015-03-30 23:55                       ` Marcelo Tosatti
2015-03-31  1:13                         ` Wu, Feng
2015-04-14  7:37                         ` Wu, Feng
2015-06-05 21:59                           ` Marcelo Tosatti
2015-06-08  1:43                             ` Wu, Feng
2014-12-12 15:14 ` [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set Feng Wu
2014-12-17 17:42   ` Paolo Bonzini
2014-12-18  3:14     ` Wu, Feng
2014-12-18  8:38       ` Paolo Bonzini
2014-12-18 15:09         ` Zhang, Yang Z
2014-12-19  2:58           ` Wu, Feng
2014-12-19  3:32             ` Zhang, Yang Z
2014-12-19  4:34               ` Wu, Feng
2014-12-19  4:44                 ` Zhang, Yang Z
2014-12-19  4:49                   ` Wu, Feng
2014-12-19  5:25                     ` Zhang, Yang Z
2014-12-19  5:46                       ` Wu, Feng
2014-12-19  7:04                         ` Zhang, Yang Z
2014-12-19 12:00                       ` Paolo Bonzini
2014-12-19 23:34                         ` Wu, Feng
2014-12-12 15:15 ` [v3 26/26] iommu/vt-d: Add a command line parameter for VT-d posted-interrupts Feng Wu
2015-01-28 15:39   ` David Woodhouse
2014-12-16  9:04 ` [v3 00/26] Add VT-d Posted-Interrupts support Wu, Feng
2015-01-06  1:10 ` Wu, Feng
2015-01-09 12:46   ` joro
2015-01-09 13:58     ` Wu, Feng
2015-01-21  2:25 ` Wu, Feng
2015-01-28  3:01   ` Wu, Feng
2015-01-28  3:44     ` Alex Williamson
2015-01-28  4:44       ` Wu, Feng
     [not found] <1415059685.1337085.1419266271242.JavaMail.zimbra@zmail13.collab.prod.int.phx2.redhat.com>
2014-12-23  0:46 ` [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI Zhang, Yang Z

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