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From: "Laszlo Ersek" <lersek@redhat.com>
To: edk2-devel-groups-io <devel@edk2.groups.io>
Cc: edk2-rfc-groups-io <rfc@edk2.groups.io>,
	qemu devel list <qemu-devel@nongnu.org>,
	Igor Mammedov <imammedo@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Jiewen Yao <jiewen.yao@intel.com>,
	Yingwen Chen <yingwen.chen@intel.com>,
	Jun Nakajima <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: CPU hotplug using SMM with QEMU+OVMF
Date: Tue, 13 Aug 2019 18:18:23 +0200	[thread overview]
Message-ID: <55cc7921-2b91-5060-d5de-d7513067f76e@redhat.com> (raw)
In-Reply-To: <effa5e32-be1e-4703-4419-8866b7754e2d@redhat.com>

On 08/13/19 18:09, Laszlo Ersek wrote:
> On 08/13/19 16:16, Laszlo Ersek wrote:

>> (06) Host CPU: (SMM) Save 38000, Update 38000 -- fill simple SMM
>>      rebase code.
>>
>> (07) Host CPU: (SMM) Send message to New CPU to Enable SMI.
> 
> Aha, so this is the SMM-only register you mention in step (03). Is the
> register specified in the Intel SDM?
> 
> 
>> (08) New CPU: (Flash) Get message - Enable SMI.
>>
>> (09) Host CPU: (SMM) Send SMI to the new CPU only.
>>
>> (10) New CPU: (SMM) Response first SMI at 38000, and rebase SMBASE to
>>      TSEG.
> 
> What code does the new CPU execute after it completes step (10)? Does it
> halt?
> 
> 
>> (11) Host CPU: (SMM) Restore 38000.
> 
> These steps (i.e., (06) through (11)) don't appear RAS-specific. The
> only platform-specific feature seems to be SMI masking register, which
> could be extracted into a new SmmCpuFeaturesLib API.
> 
> Thus, would you please consider open sourcing firmware code for steps
> (06) through (11)?
> 
> 
> Alternatively -- and in particular because the stack for step (01)
> concerns me --, we could approach this from a high-level, functional
> perspective. The states that really matter are the relocated SMBASE for
> the new CPU, and the state of the full system, right at the end of step
> (11).
> 
> When the SMM setup quiesces during normal firmware boot, OVMF could use
> existent (finalized) SMBASE infomation to *pre-program* some virtual
> QEMU hardware, with such state that would be expected, as "final" state,
> of any new hotplugged CPU. Afterwards, if / when the hotplug actually
> happens, QEMU could blanket-apply this state to the new CPU, and
> broadcast a hardware SMI to all CPUs except the new one.
> 
> The hardware SMI should tell the firmware that the rest of the process
> -- step (12) below, and onward -- is being requested.
> 
> If I understand right, this approach would produce an firmware & system
> state that's identical to what's expected right after step (11):
> 
> - all SMBASEs relocated
> - all preexistent CPUs in SMM
> - new CPU halted / blocked from launch
> - DRAM at 0x30000 / 0x38000 contains OS-owned data
> 
> Is my understanding correct that this is the expected state after step
> (11)?

Revisiting some of my notes from earlier, such as
<https://bugzilla.redhat.com/show_bug.cgi?id=1454803#c46> -- apologies,
private BZ... --, we discussed some of this stuff with Mike on the phone
in April.

And, it looked like generating a hardware SMI in QEMU, in association
with the hotplug action that was being requested through the QEMU
monitor, would be the right approach.

By now I have forgotten about that discussion -- hence "revisiting my
notes"--, but luckily, it seems consistent with what I've proposed
above, under "alternatively".

Thanks,
Laszlo

  reply	other threads:[~2019-08-13 16:18 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 [this message]
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                                                 ` [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF Laszlo Ersek
2019-08-27 16:23                                                   ` 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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