From: Peter Krempa <pkrempa@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v2 01/14] KVM: x86: change PIT discard tick policy
Date: Thu, 25 Feb 2016 13:34:29 +0100 [thread overview]
Message-ID: <20160225123429.GD5757@andariel.pipo.sk> (raw)
In-Reply-To: <20160219144422.GA2456@potion.brq.redhat.com>
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On Fri, Feb 19, 2016 at 15:44:23 +0100, Radim Krčmář wrote:
> [Cc'd Peter, the last guy that touched timers in libvirt, because he
> might know what tick policies are supposed to be.]
I found the following RFC that describes the design of timer access in
libvirt:
http://www.redhat.com/archives/libvir-list/2010-March/msg00304.html
>
> 2016-02-18 18:55+0100, Paolo Bonzini:
> > On 18/02/2016 18:33, Paolo Bonzini wrote:
> >> On 18/02/2016 17:56, Radim Krčmář wrote:
> >>> 2016-02-18 17:13+0100, Paolo Bonzini:
> >>>> On 17/02/2016 20:14, Radim Krčmář wrote:
> >>>>> Discard policy uses ack_notifiers to prevent injection of PIT interrupts
> >>>>> before EOI from the last one.
> >>>>>
> >>>>> This patch changes the policy to always try to deliver the interrupt,
> >>>>> which makes a difference when its vector is in ISR.
> >>>>> Old implementation would drop the interrupt, but proposed one injects to
> >>>>> IRR, like real hardware would.
> >>>>
> >>>> This seems like what libvirt calls the "merge" policy:
> >>>
> >>> Oops, I never looked beyond QEMU after seeing that the naming in libvirt
> >>> doesn't even match ...
> >>>
> >>> I think the policy that KVM implements (which I call discard) is "delay"
> >>> in libvirt. (https://libvirt.org/formatdomain.html#elementsTime)
>
> (I looked at libvirt code, but couldn't find any use of merge or discard
> policies, so please bear with me as I disagree wherever it's possible.)
Indeed, it looks like it never was implemented. Unfortunately i'm not
able to assist more in this case.
Peter
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next prev parent reply other threads:[~2016-02-25 12:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-17 19:14 [PATCH v2 00/14] KVM: x86: change PIT discard policy and untangle related code Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 01/14] KVM: x86: change PIT discard tick policy Radim Krčmář
2016-02-18 16:13 ` Paolo Bonzini
2016-02-18 16:56 ` Radim Krčmář
2016-02-18 17:33 ` Paolo Bonzini
2016-02-18 17:55 ` Paolo Bonzini
2016-02-19 14:44 ` Radim Krčmář
2016-02-25 12:34 ` Peter Krempa [this message]
2016-02-25 13:38 ` Paolo Bonzini
2016-02-25 17:36 ` Radim Krčmář
2016-02-25 19:11 ` Paolo Bonzini
2016-02-26 13:44 ` Radim Krčmář
2016-02-18 18:49 ` Paolo Bonzini
2016-02-17 19:14 ` [PATCH v2 02/14] KVM: x86: simplify atomics in kvm_pit_ack_irq Radim Krčmář
2016-02-18 18:04 ` Paolo Bonzini
2016-02-19 15:51 ` Radim Krčmář
2016-02-19 15:56 ` Paolo Bonzini
2016-02-17 19:14 ` [PATCH v2 03/14] KVM: x86: add kvm_pit_reset_reinject Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 04/14] KVM: x86: use atomic_t instead of pit.inject_lock Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 05/14] KVM: x86: tone down WARN_ON pit.state_lock Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 06/14] KVM: x86: pass struct kvm_pit instead of kvm in PIT Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 07/14] KVM: x86: remove unnecessary uses of PIT state lock Radim Krčmář
2016-02-18 18:03 ` Paolo Bonzini
2016-02-19 14:45 ` Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard policy Radim Krčmář
2016-02-18 18:05 ` Paolo Bonzini
2016-02-18 18:08 ` Paolo Bonzini
2016-02-19 15:04 ` Radim Krčmář
2016-02-19 15:06 ` Paolo Bonzini
2016-02-19 15:09 ` Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 09/14] KVM: x86: refactor kvm_create_pit Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 10/14] KVM: x86: refactor kvm_free_pit Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 11/14] KVM: x86: remove pit and kvm from kvm_kpit_state Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 12/14] KVM: x86: remove pointless dereference of PIT Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 13/14] KVM: x86: don't assume layout of kvm_kpit_state Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 14/14] KVM: x86: move PIT timer function initialization Radim Krčmář
2016-02-18 18:11 ` [PATCH v2 00/14] KVM: x86: change PIT discard policy and untangle related code Paolo Bonzini
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