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From: Marc Zyngier <marc.zyngier@arm.com>
To: David Hildenbrand <david@redhat.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Igor Mammedov <imammedo@redhat.com>
Cc: Christoffer Dall <cdall@cs.columbia.edu>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Christoffer Dall <christofferdall@christofferdall.dk>,
	qemu-arm <qemu-arm@nongnu.org>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [Qemu-devel] [Qemu-arm] VCPU hotplug on KVM/ARM
Date: Wed, 7 Mar 2018 12:47:39 +0000	[thread overview]
Message-ID: <acd04e77-33c9-71f1-c140-1f9c20da8022@arm.com> (raw)
In-Reply-To: <b049a501-cd5e-8c22-9c62-88c950e01b1b@redhat.com>

On 01/03/18 13:32, David Hildenbrand wrote:
> On 01.03.2018 11:05, Peter Maydell wrote:
>> On 1 March 2018 at 09:50, Igor Mammedov <imammedo@redhat.com> wrote:
>>> In QEMU on x86 (and I think ppc, s390 as well), we create vCPUs on demand.>>
>>> It would be nice if ARM would be able to do that too,
>>> so that it could take advantage of the same code.
>>
>> It's not clear to me how that would work, given that for
>> instance the interrupt controller wants to know up-front
>> how many CPUs it has to deal with.
>>
> 
> So how is cpu hotplug handled in HW? Or doesn't it even exist there?

I don't know of any physical system offering that facility.

> (we have max_cpus for the interrupt controller, but not sure if that is
> what we want)
We'd need something along those lines. Each CPU has a notional point to
point link to the interrupt controller (to the redistributor, to be
precise), and this entity must pre-exist.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <marc.zyngier@arm.com>
To: David Hildenbrand <david@redhat.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Igor Mammedov <imammedo@redhat.com>
Cc: Christoffer Dall <cdall@cs.columbia.edu>,
	Christoffer Dall <christofferdall@christofferdall.dk>,
	QEMU Developers <qemu-devel@nongnu.org>,
	qemu-arm <qemu-arm@nongnu.org>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [Qemu-devel] [Qemu-arm] VCPU hotplug on KVM/ARM
Date: Wed, 7 Mar 2018 12:47:39 +0000	[thread overview]
Message-ID: <acd04e77-33c9-71f1-c140-1f9c20da8022@arm.com> (raw)
In-Reply-To: <b049a501-cd5e-8c22-9c62-88c950e01b1b@redhat.com>

On 01/03/18 13:32, David Hildenbrand wrote:
> On 01.03.2018 11:05, Peter Maydell wrote:
>> On 1 March 2018 at 09:50, Igor Mammedov <imammedo@redhat.com> wrote:
>>> In QEMU on x86 (and I think ppc, s390 as well), we create vCPUs on demand.>>
>>> It would be nice if ARM would be able to do that too,
>>> so that it could take advantage of the same code.
>>
>> It's not clear to me how that would work, given that for
>> instance the interrupt controller wants to know up-front
>> how many CPUs it has to deal with.
>>
> 
> So how is cpu hotplug handled in HW? Or doesn't it even exist there?

I don't know of any physical system offering that facility.

> (we have max_cpus for the interrupt controller, but not sure if that is
> what we want)
We'd need something along those lines. Each CPU has a notional point to
point link to the interrupt controller (to the redistributor, to be
precise), and this entity must pre-exist.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

  reply	other threads:[~2018-03-07 12:47 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-27  9:31 VCPU hotplug on KVM/ARM bthakur
2018-02-27 10:47 ` Christoffer Dall
2018-02-27 12:04   ` bthakur
2018-02-27 12:46     ` Christoffer Dall
2018-02-27 13:21       ` [Qemu-devel] " Andrew Jones
2018-02-27 13:21         ` Andrew Jones
2018-03-01  9:50         ` [Qemu-devel] " Igor Mammedov
2018-03-01  9:50           ` Igor Mammedov
2018-03-01 10:05           ` [Qemu-devel] [Qemu-arm] " Peter Maydell
2018-03-01 10:05             ` [Qemu-arm] [Qemu-devel] " Peter Maydell
2018-03-01 13:32             ` [Qemu-devel] [Qemu-arm] " David Hildenbrand
2018-03-01 13:32               ` David Hildenbrand
2018-03-07 12:47               ` Marc Zyngier [this message]
2018-03-07 12:47                 ` Marc Zyngier
2018-07-24 18:35         ` [Qemu-devel] " Maran Wilson
2018-07-24 18:35           ` Maran Wilson
2018-07-25  6:45           ` [Qemu-devel] " Igor Mammedov
2018-07-25  6:45             ` Igor Mammedov
2018-07-25 10:40           ` Marc Zyngier
2018-07-25 10:40             ` Marc Zyngier
2018-07-25 12:28             ` [Qemu-devel] " Andrew Jones
2018-07-25 12:28               ` Andrew Jones
2018-07-25 13:07               ` Marc Zyngier
2018-07-25 13:07                 ` Marc Zyngier
2018-07-25 17:26                 ` Maran Wilson
2018-07-25 17:26                   ` Maran Wilson
2018-07-31 10:27                 ` Igor Mammedov
2018-07-31 10:27                   ` Igor Mammedov
2018-07-31 10:57                   ` David Hildenbrand
2018-07-31 10:57                     ` David Hildenbrand
2018-08-01  8:09                   ` Bharata B Rao
2018-08-01  8:09                     ` Bharata B Rao

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