From: Andrew Cooper <andrew.cooper3@citrix.com>
To: 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 13:16:33 +0100 [thread overview]
Message-ID: <55952BA1.6050701@citrix.com> (raw)
In-Reply-To: <1435838657.25170.462.camel@citrix.com>
On 02/07/15 13:04, Dario Faggioli wrote:
> On Thu, 2015-07-02 at 11:30 +0100, Andrew Cooper wrote:
>> On 02/07/15 09:30, Dario Faggioli wrote:
>>> 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
>>
> Right, I see it now, thanks.
>
>> 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.
>>
> Well, given the thing works as you (two) just described, I think
> draining the list is the only thing we can do.
>
> In fact, AFAICT, since we can't know for what vcpu a particular
> notification is intended, we don't have alternatives to waking them all,
> do we?
Perhaps you misunderstand.
Every single vcpu has a PI descriptor which is shared memory with hardware.
A NV is delivered strictly when hardware atomically changes desc.on from
0 to 1. i.e. the first time that an oustanding notification arrives.
(iirc, desc.on is later cleared by hardware when the vcpu is scheduled
and the vector(s) actually injected.)
Part of the scheduling modifications alter when a vcpu is eligible to
have NV's delivered on its behalf. non-scheduled vcpus get NV's while
scheduled vcpus have direct injection instead.
Therefore, in the case that an NV arrives, we know for certain that one
of the NV-eligible vcpus has had desc.on set by hardware, and we can
uniquely identify it by searching for the vcpu for which desc.on is set.
In the case of stacked NV's, we cannot associate which specific vcpu
caused which NV, but we know that we will get one NV per vcpu needing
kicking.
~Andrew
next prev parent reply other threads:[~2015-07-02 12:16 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
2015-07-02 12:04 ` Dario Faggioli
2015-07-02 12:10 ` Wu, Feng
2015-07-02 12:16 ` Andrew Cooper [this message]
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
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