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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Jan Beulich <JBeulich@suse.com>, roger.pau@citrix.com
Cc: Juergen Gross <JGross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Al Stone <al.stone@linaro.org>,
	Graeme Gregory <graeme.gregory@linaro.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Anshul Makkar <anshul.makkar@citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	xen-devel@lists.xenproject.org
Subject: Re: PVH CPU hotplug design document
Date: Mon, 23 Jan 2017 11:24:19 -0500	[thread overview]
Message-ID: <93a8c600-d746-7847-a997-c855dd3a9a9c@oracle.com> (raw)
In-Reply-To: <588636260200007800132F40@prv-mh.provo.novell.com>

On 01/23/2017 10:58 AM, Jan Beulich wrote:
>>>> On 23.01.17 at 16:49, <boris.ostrovsky@oracle.com> wrote:
>> On 01/23/2017 10:43 AM, Boris Ostrovsky wrote:
>>>>> From Linux perspective one option could be to have domU with PV-style
>>>>> vCPU on/offlining based on xenstore and switch to ACPI hotplug if/when
>>>>> it becomes available. This, however, will need an indication from the
>>>>> hypervisor. We could, for example, set ACPI_FADT_HW_REDUCED, as we
>>>>> discussed earlier.
>>>> I think we shouldn't overload that flag. Didn't we settle already on using
>>>> two CPUID flags (of for PV-style onlining/offlining, the other for ACPI
>>>> hot(un)plug)? With that I think I could then be talked into accepting the
>>>> existence of two different models (and kernels could pick which one(s)
>>>> they would like to support).
>>> I forgot about existence of ACPI_FADT_HW_REDUCED until this morning,
>>> which is why I mentioned it now.
>>>
>>> We can go with CPUID flags although I am not sure why we'd need two. I'd
>>> think that OS can be expected to always support PV-style so the flag
>>> would indicate support for ACPI-based hotplug.
>> In fact, it doesn't matter whether OS supports PV-style hotplug. It's
>> that Xen will always set appropriate xenstore entry. It's up to the OS
>> whether to watch it and act upon this.
> That's a good point, perhaps just one CPUID flag will do then indeed.

Roger, are you going to include this in your patchset or do you want me
to do it?

-boris


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  reply	other threads:[~2017-01-23 16:24 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-12 12:13 PVH CPU hotplug design document Roger Pau Monné
2017-01-12 19:00 ` Andrew Cooper
2017-01-13  3:06   ` Boris Ostrovsky
2017-01-13 15:27   ` Jan Beulich
2017-01-16 14:59     ` Roger Pau Monné
2017-01-16 14:50   ` Roger Pau Monné
2017-01-13 15:51 ` Jan Beulich
2017-01-13 19:41   ` Stefano Stabellini
2017-01-14  1:44   ` Boris Ostrovsky
2017-01-16 11:03     ` Jan Beulich
2017-01-16 15:14   ` Roger Pau Monné
2017-01-16 16:09     ` Jan Beulich
2017-01-16 16:31       ` Roger Pau Monné
2017-01-16 16:50         ` Jan Beulich
2017-01-16 17:44           ` Roger Pau Monné
2017-01-16 18:16             ` Stefano Stabellini
2017-01-17  9:12             ` Jan Beulich
2017-01-17 11:43               ` Roger Pau Monné
2017-01-17 12:33                 ` Jan Beulich
2017-01-17 14:13                   ` Roger Pau Monné
2017-01-17 14:44                     ` Jan Beulich
2017-01-17 15:27                       ` Boris Ostrovsky
2017-01-17 15:33                         ` Jan Beulich
2017-01-17 15:50                           ` Boris Ostrovsky
2017-01-17 17:45                             ` Roger Pau Monné
2017-01-17 18:50                               ` Boris Ostrovsky
2017-01-18 10:34                                 ` Roger Pau Monné
2017-01-18 10:44                                   ` Jan Beulich
2017-01-18 11:54                                     ` Roger Pau Monné
2017-01-18 13:25                                       ` Jan Beulich
2017-01-22 18:39                                         ` Boris Ostrovsky
2017-01-23 10:35                                           ` Jan Beulich
2017-01-23 14:28                                             ` Boris Ostrovsky
2017-01-23 15:17                                               ` Jan Beulich
2017-01-23 15:43                                                 ` Boris Ostrovsky
2017-01-23 15:49                                                   ` Boris Ostrovsky
2017-01-23 15:58                                                     ` Jan Beulich
2017-01-23 16:24                                                       ` Boris Ostrovsky [this message]
2017-01-23 16:50                                                         ` Roger Pau Monné
2017-01-23 17:05                                                           ` Boris Ostrovsky
2017-01-23 17:14                                                             ` Roger Pau Monné
2017-01-23 18:36                                                               ` Boris Ostrovsky
2017-01-24  7:43                                                                 ` Jan Beulich
2017-01-24 14:15                                                                   ` Boris Ostrovsky
2017-01-23 15:49                                                   ` Jan Beulich
2017-01-18 13:34                                       ` Boris Ostrovsky

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