From: "Laszlo Ersek" <lersek@redhat.com>
To: "Kinney, Michael D" <michael.d.kinney@intel.com>,
"Yao, Jiewen" <jiewen.yao@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"rfc@edk2.groups.io" <rfc@edk2.groups.io>
Cc: Alex Williamson <alex.williamson@redhat.com>,
"devel@edk2.groups.io" <devel@edk2.groups.io>,
qemu devel list <qemu-devel@nongnu.org>,
Igor Mammedov <imammedo@redhat.com>,
"Chen, Yingwen" <yingwen.chen@intel.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Joao Marcal Lemos Martins <joao.m.martins@oracle.com>,
Phillip Goerl <phillip.goerl@oracle.com>
Subject: Re: [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF
Date: Mon, 26 Aug 2019 17:30:43 +0200 [thread overview]
Message-ID: <ea0330f1-cb6a-2a45-f8e7-3de19b117e77@redhat.com> (raw)
In-Reply-To: <E92EE9817A31E24EB0585FDF735412F5B9DA25CC@ORSMSX113.amr.corp.intel.com>
On 08/23/19 17:25, Kinney, Michael D wrote:
> Hi Jiewen,
>
> If a hot add CPU needs to run any code before the
> first SMI, I would recommend is only executes code
> from a write protected FLASH range without a stack
> and then wait for the first SMI.
"without a stack" looks very risky to me. Even if we manage to implement
the guest code initially, we'll be trapped without a stack, should we
ever need to add more complex stuff there.
> For this OVMF use case, is any CPU init required
> before the first SMI?
I expressed a preference for that too: "I wish we could simply wake the
new CPU [...] with an SMI".
http://mid.mail-archive.com/398b3327-0820-95af-a34d-1a4a1d50cf35@redhat.com
> From Paolo's list of steps are steps (8a) and (8b)
> really required?
See again my message linked above -- just after the quoted sentence, I
wrote, "IOW, if we could excise steps 07b, 08a, 08b".
But, I obviously defer to Paolo and Igor on that.
(I do believe we have a dilemma here. In QEMU, we probably prefer to
emulate physical hardware as faithfully as possible. However, we do not
have Cache-As-RAM (nor do we intend to, IIUC). Does that justify other
divergences from physical hardware too, such as waking just by virtue of
an SMI?)
> Can the SMI monarch use the Local
> APIC to send a directed SMI to the hot added CPU?
> The SMI monarch needs to know the APIC ID of the
> hot added CPU. Do we also need to handle the case
> where multiple CPUs are added at once? I think we
> would need to serialize the use of 3000:8000 for the
> SMM rebase operation on each hot added CPU.
I agree this would be a huge help.
> It would be simpler if we can guarantee that only
> one CPU can be added or removed at a time and the
> complete flow of adding a CPU to SMM and the OS
> needs to be completed before another add/remove
> event needs to be processed.
I don't know if the QEMU monitor command in question can guarantee this
serialization. I think such a request/response pattern is generally
implementable between QEMU and guest code.
But, AIUI, the "device-add" monitor command is quite generic, and used
for hot-plugging a number of other (non-CPU) device models. I'm unsure
if the pattern in question can be squeezed into "device-add". (It's not
a dedicated command for CPU hotplug.)
... Apologies that I didn't add much information to the thread, just
now. I'd like to keep the discussion going.
Thanks
Laszlo
next prev parent reply other threads:[~2019-08-26 15:30 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 14:16 CPU hotplug using SMM with QEMU+OVMF Laszlo Ersek
2019-08-13 16:09 ` Laszlo Ersek
2019-08-13 16:18 ` Laszlo Ersek
2019-08-14 13:20 ` Yao, Jiewen
2019-08-14 14:04 ` Paolo Bonzini
2019-08-15 9:55 ` Yao, Jiewen
2019-08-15 16:04 ` Paolo Bonzini
2019-08-15 15:00 ` [edk2-devel] " Laszlo Ersek
2019-08-15 16:16 ` Igor Mammedov
2019-08-15 16:21 ` Paolo Bonzini
2019-08-16 2:46 ` Yao, Jiewen
2019-08-16 7:20 ` Paolo Bonzini
2019-08-16 7:49 ` Yao, Jiewen
2019-08-16 20:15 ` Laszlo Ersek
2019-08-16 22:19 ` Alex Williamson
2019-08-17 0:20 ` Yao, Jiewen
2019-08-18 19:50 ` Paolo Bonzini
2019-08-18 23:00 ` Yao, Jiewen
2019-08-19 14:10 ` Paolo Bonzini
2019-08-21 12:07 ` Laszlo Ersek
2019-08-21 15:48 ` [edk2-rfc] " Michael D Kinney
2019-08-21 17:05 ` Paolo Bonzini
2019-08-21 17:25 ` Michael D Kinney
2019-08-21 17:39 ` Paolo Bonzini
2019-08-21 20:17 ` Michael D Kinney
2019-08-22 6:18 ` Paolo Bonzini
2019-08-22 18:29 ` Laszlo Ersek
2019-08-22 18:51 ` Paolo Bonzini
2019-08-23 14:53 ` Laszlo Ersek
2019-08-22 20:13 ` Michael D Kinney
2019-08-22 17:59 ` Laszlo Ersek
2019-08-22 18:43 ` Paolo Bonzini
2019-08-22 20:06 ` Michael D Kinney
2019-08-22 22:18 ` Paolo Bonzini
2019-08-22 22:32 ` Michael D Kinney
2019-08-22 23:11 ` Paolo Bonzini
2019-08-23 1:02 ` Michael D Kinney
2019-08-23 5:00 ` Yao, Jiewen
2019-08-23 15:25 ` Michael D Kinney
2019-08-24 1:48 ` Yao, Jiewen
2019-08-27 18:31 ` Igor Mammedov
2019-08-29 17:01 ` Laszlo Ersek
2019-08-30 14:48 ` Igor Mammedov
2019-08-30 18:46 ` Laszlo Ersek
2019-09-02 8:45 ` Igor Mammedov
2019-09-02 19:09 ` Laszlo Ersek
2019-09-03 14:53 ` [Qemu-devel] " Igor Mammedov
2019-09-03 17:20 ` Laszlo Ersek
2019-09-04 9:52 ` imammedo
2019-09-05 13:08 ` Laszlo Ersek
2019-09-05 15:45 ` Igor Mammedov
2019-09-05 15:49 ` [PATCH] q35: lpc: allow to lock down 128K RAM at default SMBASE address Igor Mammedov
2019-09-09 19:15 ` Laszlo Ersek
2019-09-09 19:20 ` Laszlo Ersek
2019-09-10 15:58 ` Igor Mammedov
2019-09-11 17:30 ` Laszlo Ersek
2019-09-17 13:11 ` [edk2-devel] " Igor Mammedov
2019-09-17 14:38 ` [staging/branch]: CdePkg - C Development Environment Package Minnow Ware
2019-08-26 15:30 ` Laszlo Ersek [this message]
2019-08-27 16:23 ` [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF Igor Mammedov
2019-08-27 20:11 ` Laszlo Ersek
2019-08-28 12:01 ` Igor Mammedov
2019-08-29 16:25 ` Laszlo Ersek
2019-08-30 13:49 ` [Qemu-devel] " Igor Mammedov
2019-08-22 17:53 ` Laszlo Ersek
2019-08-16 20:00 ` Laszlo Ersek
2019-08-15 16:07 ` Igor Mammedov
2019-08-15 16:24 ` Paolo Bonzini
2019-08-16 7:42 ` Igor Mammedov
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