From: "Wu, Feng" <feng.wu@intel.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Dario Faggioli <dario.faggioli@citrix.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
"keir@xen.org" <keir@xen.org>,
"george.dunlap@eu.citrix.com" <george.dunlap@eu.citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
"jbeulich@suse.com" <jbeulich@suse.com>,
"Zhang, Yang Z" <yang.z.zhang@intel.com>,
"Wu, Feng" <feng.wu@intel.com>
Subject: Re: [v3 12/15] vmx: posted-interrupt handling when vCPU is blocked
Date: Thu, 2 Jul 2015 10:56:11 +0000 [thread overview]
Message-ID: <E959C4978C3B6342920538CF579893F0025E4B20@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <559512BC.90303@citrix.com>
> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
> Sent: Thursday, July 02, 2015 6:30 PM
> To: Dario Faggioli; Wu, Feng
> Cc: xen-devel@lists.xen.org; Zhang, Yang Z; george.dunlap@eu.citrix.com;
> Tian, Kevin; keir@xen.org; jbeulich@suse.com
> Subject: Re: [Xen-devel] [v3 12/15] vmx: posted-interrupt handling when vCPU
> is blocked
>
> On 02/07/15 09:30, Dario Faggioli wrote:
> > On Thu, 2015-07-02 at 04:27 +0000, Wu, Feng wrote:
> >
> >>>>> + list_for_each_entry(vmx, &per_cpu(pi_blocked_vcpu, cpu),
> >>>>> + pi_blocked_vcpu_list)
> >>>>> + if ( vmx->pi_desc.on )
> >>>>> + tasklet_schedule(&vmx->pi_vcpu_wakeup_tasklet);
> >>>> There is a logical bug here. If we have two NV's delivered to this
> >>>> pcpu, we will kick the first vcpu twice.
> >>>>
> >>>> On finding desc.on, a kick should be scheduled, then the vcpu removed
> >>>> from this list. With desc.on set, we know for certain that another NV
> >>>> will not arrive for it until it has been scheduled again and the
> >>>> interrupt posted.
> >>>>
> >>> Yes, that seems a possible issue (and one that should indeed be
> >>> avoided).
> >>>
> >>> I'm still unsure about the one that I raised myself but, if it is
> >>> possible to have more than one vcpu in a pcpu list, with desc.on==true,
> >>> then it looks to me that we kick all of them, for each notification.
> >>>
> >>> Added what Andrew's spotted, if there are a bunch of vcpus, queued with
> >>> desc.on==ture, and a bunch of notifications arrives before the tasklet
> >>> gets executed, we'll be kicking the whole bunch of them for a bunch of
> >>> times! :-/
> >> As Andrew mentioned, removing the vCPUs with desc.on = true from the
> >> list can avoid kick vCPUs for multiple times.
> >>
> > It avoids kicking vcpus multiple times if more than one notification
> > arrives, yes.
> >
> > It is, therefore, not effective in making sure that, even with only one
> > notification, you only kick the interested vcpu.
> >
> > This is the third time that I ask:
> > (1) whether it is possible to have more vcpus queued on one pcpu PI
> > blocked list with desc.on (I really believe it is);
> > (2) if yes, whether it is TheRightThing(TM) to kick all of them, as
> > soon as any notification arrives, instead that putting together a
> > mechanism for kicking only a specific one.
>
> We will receive one NV for every time the hardware managed to
> successfully set desc.on
>
> If multiple stack up and we proactively drain the list, we will
> subsequently search the list to completion for all remaining NV's, due
> to finding no appropriate entries.
>
> I can't currently decide whether this will be quicker or slower overall,
> or (most likely) it will even out to equal in the general case.
What do you mean by "general case"?
Thanks,
Feng
>
> ~Andrew
next prev parent reply other threads:[~2015-07-02 10:56 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-24 5:18 [v3 00/15] Add VT-d Posted-Interrupts support Feng Wu
2015-06-24 5:18 ` [v3 01/15] Vt-d Posted-intterrupt (PI) design Feng Wu
2015-06-24 6:15 ` Meng Xu
2015-06-24 6:19 ` Wu, Feng
2015-07-08 7:21 ` Tian, Kevin
2015-07-08 7:29 ` Wu, Feng
2015-06-24 5:18 ` [v3 02/15] Add helper macro for X86_FEATURE_CX16 feature detection Feng Wu
2015-06-24 17:31 ` Andrew Cooper
2015-07-08 7:23 ` Tian, Kevin
2015-06-24 5:18 ` [v3 03/15] Add cmpxchg16b support for x86-64 Feng Wu
2015-06-24 18:35 ` Andrew Cooper
2015-07-08 7:06 ` Wu, Feng
2015-07-08 8:12 ` Jan Beulich
2015-07-08 8:33 ` Wu, Feng
2015-07-08 8:43 ` Jan Beulich
2015-07-08 8:50 ` Wu, Feng
2015-07-08 8:50 ` Andrew Cooper
2015-07-10 12:57 ` Jan Beulich
2015-06-24 5:18 ` [v3 04/15] iommu: Add iommu_intpost to control VT-d Posted-Interrupts feature Feng Wu
2015-06-25 9:06 ` Andrew Cooper
2015-06-25 9:47 ` Wu, Feng
2015-06-25 10:16 ` Andrew Cooper
2015-06-25 12:47 ` Wu, Feng
2015-07-08 7:30 ` Tian, Kevin
2015-06-24 5:18 ` [v3 05/15] vt-d: VT-d Posted-Interrupts feature detection Feng Wu
2015-06-25 10:21 ` Andrew Cooper
2015-06-25 13:02 ` Wu, Feng
2015-07-08 7:32 ` Tian, Kevin
2015-07-08 8:00 ` Wu, Feng
2015-06-24 5:18 ` [v3 06/15] vmx: Extend struct pi_desc to support VT-d Posted-Interrupts Feng Wu
2015-06-29 15:04 ` Andrew Cooper
2015-07-08 7:48 ` Tian, Kevin
2015-07-10 13:08 ` Jan Beulich
2015-07-15 2:40 ` Wu, Feng
2015-07-15 8:20 ` Jan Beulich
2015-07-15 8:26 ` Wu, Feng
2015-07-15 8:36 ` Jan Beulich
2015-07-15 8:43 ` Wu, Feng
2015-07-15 9:28 ` Jan Beulich
2015-07-15 9:30 ` Wu, Feng
2015-07-15 3:13 ` Wu, Feng
2015-06-24 5:18 ` [v3 07/15] vmx: Initialize VT-d Posted-Interrupts Descriptor Feng Wu
2015-06-29 15:32 ` Andrew Cooper
2015-06-30 1:46 ` Wu, Feng
2015-06-30 2:32 ` Dario Faggioli
2015-07-08 7:53 ` Tian, Kevin
2015-06-24 5:18 ` [v3 08/15] Suppress posting interrupts when 'SN' is set Feng Wu
2015-06-29 15:41 ` Andrew Cooper
2015-06-30 1:48 ` Wu, Feng
2015-07-08 9:06 ` Tian, Kevin
2015-07-08 10:11 ` Wu, Feng
2015-07-08 11:31 ` Tian, Kevin
2015-07-08 11:58 ` Wu, Feng
2015-07-10 13:20 ` Jan Beulich
2015-06-24 5:18 ` [v3 09/15] vt-d: Extend struct iremap_entry to support VT-d Posted-Interrupts Feng Wu
2015-06-29 16:04 ` Andrew Cooper
2015-06-30 1:52 ` Wu, Feng
2015-07-08 9:10 ` Tian, Kevin
2015-07-10 13:27 ` Jan Beulich
2015-06-24 5:18 ` [v3 10/15] vt-d: Add API to update IRTE when VT-d PI is used Feng Wu
2015-06-29 16:22 ` Andrew Cooper
2015-07-08 9:59 ` Tian, Kevin
2015-07-08 10:12 ` Wu, Feng
2015-07-10 14:01 ` Jan Beulich
2015-07-15 6:04 ` Wu, Feng
2015-07-15 8:24 ` Jan Beulich
2015-07-15 8:38 ` Wu, Feng
2015-07-15 8:46 ` Jan Beulich
2015-07-15 8:55 ` Wu, Feng
2015-07-15 9:32 ` Jan Beulich
2015-06-24 5:18 ` [v3 11/15] Update IRTE according to guest interrupt config changes Feng Wu
2015-06-29 16:46 ` Andrew Cooper
2015-07-08 10:22 ` Tian, Kevin
2015-07-08 10:31 ` Wu, Feng
2015-07-08 11:46 ` Tian, Kevin
2015-07-08 11:52 ` Wu, Feng
2015-07-08 11:54 ` Tian, Kevin
2015-07-10 14:23 ` Jan Beulich
2015-06-24 5:18 ` [v3 12/15] vmx: posted-interrupt handling when vCPU is blocked Feng Wu
2015-06-29 17:07 ` Andrew Cooper
2015-07-08 10:36 ` Wu, Feng
2015-07-08 10:48 ` Jan Beulich
[not found] ` <559181F9.6020106@citrix.com>
2015-06-30 2:51 ` Fwd: " Dario Faggioli
2015-06-30 2:59 ` Wu, Feng
2015-06-30 9:46 ` Dario Faggioli
2015-06-30 10:11 ` Andrew Cooper
2015-07-01 13:26 ` Dario Faggioli
2015-07-02 4:27 ` Wu, Feng
2015-07-02 8:30 ` Dario Faggioli
2015-07-02 8:58 ` Wu, Feng
2015-07-02 10:09 ` Dario Faggioli
2015-07-02 10:41 ` Wu, Feng
2015-07-02 10:30 ` Andrew Cooper
2015-07-02 10:56 ` Wu, Feng [this message]
2015-07-02 12:04 ` Dario Faggioli
2015-07-02 12:10 ` Wu, Feng
2015-07-02 12:16 ` Andrew Cooper
2015-07-02 12:38 ` Dario Faggioli
2015-07-02 12:59 ` Andrew Cooper
2015-07-03 1:33 ` Wu, Feng
2015-07-02 4:25 ` Wu, Feng
2015-07-08 11:00 ` Tian, Kevin
2015-07-08 11:02 ` Wu, Feng
2015-07-08 12:46 ` Jan Beulich
2015-07-08 13:09 ` Andrew Cooper
2015-07-08 22:49 ` Tian, Kevin
2015-07-09 7:25 ` Jan Beulich
2015-07-10 6:21 ` Wu, Feng
2015-07-10 6:32 ` Jan Beulich
2015-07-10 7:29 ` Wu, Feng
2015-07-10 8:49 ` Jan Beulich
2015-07-10 8:57 ` Wu, Feng
2015-07-08 22:31 ` Tian, Kevin
2015-06-24 5:18 ` [v3 13/15] vmx: Properly handle notification event when vCPU is running Feng Wu
2015-07-08 11:03 ` Tian, Kevin
2015-07-10 14:40 ` Jan Beulich
2015-06-24 5:18 ` [v3 14/15] Update Posted-Interrupts Descriptor during vCPU scheduling Feng Wu
[not found] ` <55918214.4030102@citrix.com>
2015-06-30 2:58 ` Fwd: " Dario Faggioli
2015-07-02 4:32 ` Wu, Feng
2015-07-02 4:34 ` Wu, Feng
2015-07-02 8:20 ` Dario Faggioli
2015-07-09 3:09 ` Wu, Feng
2015-07-09 8:18 ` Dario Faggioli
2015-07-09 11:19 ` George Dunlap
2015-07-09 11:29 ` George Dunlap
2015-07-09 11:38 ` Wu, Feng
2015-07-09 12:42 ` Dario Faggioli
2015-07-10 0:07 ` Wu, Feng
2015-07-10 12:40 ` Dario Faggioli
2015-07-10 13:47 ` Konrad Rzeszutek Wilk
2015-07-10 13:59 ` Dario Faggioli
2015-07-09 12:53 ` George Dunlap
2015-07-09 13:44 ` Jan Beulich
2015-07-09 14:18 ` Dario Faggioli
2015-07-09 14:27 ` George Dunlap
2015-07-09 14:47 ` Dario Faggioli
2015-07-10 5:59 ` Wu, Feng
2015-07-10 6:22 ` Jan Beulich
2015-07-10 11:05 ` Dario Faggioli
2015-07-14 5:44 ` Wu, Feng
2015-07-14 14:08 ` Wu, Feng
2015-07-14 14:54 ` Jan Beulich
2015-07-14 15:20 ` Dario Faggioli
2015-07-14 16:41 ` George Dunlap
2015-07-14 16:02 ` Dario Faggioli
2015-07-15 0:54 ` Wu, Feng
2015-07-17 7:46 ` Wu, Feng
2015-07-17 10:13 ` Dario Faggioli
2015-07-17 22:57 ` Wu, Feng
2015-07-18 13:43 ` Dario Faggioli
2015-07-10 0:15 ` Wu, Feng
2015-07-08 11:24 ` Tian, Kevin
2015-07-10 14:48 ` Jan Beulich
2015-06-24 5:18 ` [v3 15/15] Add a command line parameter for VT-d posted-interrupts Feng Wu
2015-07-08 11:25 ` Tian, Kevin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E959C4978C3B6342920538CF579893F0025E4B20@SHSMSX104.ccr.corp.intel.com \
--to=feng.wu@intel.com \
--cc=andrew.cooper3@citrix.com \
--cc=dario.faggioli@citrix.com \
--cc=george.dunlap@eu.citrix.com \
--cc=jbeulich@suse.com \
--cc=keir@xen.org \
--cc=kevin.tian@intel.com \
--cc=xen-devel@lists.xen.org \
--cc=yang.z.zhang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.