From: "Ankur Arora" <ankur.a.arora@oracle.com>
To: Laszlo Ersek <lersek@redhat.com>, devel@edk2.groups.io
Cc: imammedo@redhat.com, boris.ostrovsky@oracle.com,
Jordan Justen <jordan.l.justen@intel.com>,
Ard Biesheuvel <ard.biesheuvel@arm.com>,
Aaron Young <aaron.young@oracle.com>
Subject: Re: [PATCH v6 9/9] OvmfPkg/SmmControl2Dxe: negotiate CPU hot-unplug
Date: Wed, 3 Feb 2021 19:04:35 -0800 [thread overview]
Message-ID: <16956b08-c45d-fdf6-5283-c66130713781@oracle.com> (raw)
In-Reply-To: <b2360673-783d-cdf9-eb76-1e2200fead93@redhat.com>
On 2021-02-03 12:45 p.m., Laszlo Ersek wrote:
> On 02/03/21 06:46, Ankur Arora wrote:
>> On 2021-02-01 9:37 a.m., Laszlo Ersek wrote:
>
>>> (6) Please drop this hunk. We don't try to be smarter than QEMU, in
>>> general, whenever we perform feature negotiation.
>>
>> Also, AFAICS, we will do the hotplug (and now hot-unplug) even if it wasn't
>> negotiated?
>
> Yes, totally. We don't try to "evict" CpuHotplugSmm in case the related
> features are not supported/offered by QEMU, we'll just leave
> CpuHotplugSmm unused.
>
> Here's why: the SMI feature negotiation interface is locked down at a
> certain point; the negotiation of all of the feature bits needs to
> happen centrally, in a common spot; and it would require a really quirky
> solution in the firmware to let independent drivers negotiate *subsets*
> of the features.
Right, I see your point. Firmware doesn't really get to stand on
ceremony when HW asks it to do stuff.
Thanks
Ankur
>
> You have correctly determined that SmmControl2Dxe, the runtime DXE
> driver that produces EFI_SMM_CONTROL2_PROTOCOL, has nothing much to do
> with CPU hot-(un)plug. It's just that this is the driver that first
> used, and therefore now *owns*, the SMI feature negotiation. (See commit
> 5ba203b54e59 ("OvmfPkg/SmmControl2Dxe: negotiate
> ICH9_LPC_SMI_F_CPU_HOTPLUG", 2020-08-24).)
>
> So, to reformulate your question/statement: the firmware will retain the
> ability to do hot-(un)plug even if QEMU doesn't contain (or enable)
> those particular features.
>
> Thanks
> Laszlo
>
prev parent reply other threads:[~2021-02-04 3:04 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 0:59 [PATCH v6 0/9] support CPU hot-unplug Ankur Arora
2021-01-29 0:59 ` [PATCH v6 1/9] OvmfPkg/CpuHotplugSmm: refactor hotplug logic Ankur Arora
2021-01-30 1:15 ` [edk2-devel] " Laszlo Ersek
2021-02-02 6:19 ` Ankur Arora
2021-02-01 2:59 ` Laszlo Ersek
2021-01-29 0:59 ` [PATCH v6 2/9] OvmfPkg/CpuHotplugSmm: collect hot-unplug events Ankur Arora
2021-01-30 2:18 ` Laszlo Ersek
2021-01-30 2:23 ` Laszlo Ersek
2021-02-02 6:03 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 3/9] OvmfPkg/CpuHotplugSmm: add Qemu Cpu Status helper Ankur Arora
2021-01-30 2:36 ` Laszlo Ersek
2021-02-02 6:04 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 4/9] OvmfPkg/CpuHotplugSmm: introduce UnplugCpus() Ankur Arora
2021-01-30 2:37 ` Laszlo Ersek
2021-02-01 3:13 ` Laszlo Ersek
2021-02-03 4:28 ` Ankur Arora
2021-02-03 19:20 ` Laszlo Ersek
2021-01-29 0:59 ` [PATCH v6 5/9] OvmfPkg/CpuHotplugSmm: define CPU_HOT_EJECT_DATA Ankur Arora
2021-02-01 4:53 ` Laszlo Ersek
2021-02-02 6:15 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 6/9] OvmfPkg/SmmCpuFeaturesLib: init CPU ejection state Ankur Arora
2021-02-01 13:36 ` Laszlo Ersek
2021-02-03 5:20 ` Ankur Arora
2021-02-03 20:36 ` Laszlo Ersek
2021-02-04 2:58 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 7/9] OvmfPkg/CpuHotplugSmm: add CpuEject() Ankur Arora
2021-02-01 16:11 ` Laszlo Ersek
2021-02-01 19:08 ` Laszlo Ersek
2021-02-01 20:12 ` Ankur Arora
2021-02-02 14:00 ` Laszlo Ersek
2021-02-02 14:15 ` Laszlo Ersek
2021-02-03 6:45 ` Ankur Arora
2021-02-03 20:58 ` Laszlo Ersek
2021-02-04 2:49 ` Ankur Arora
2021-02-04 8:58 ` Laszlo Ersek
2021-02-05 16:06 ` [edk2-devel] " Laszlo Ersek
2021-02-08 5:04 ` Ankur Arora
2021-02-03 6:13 ` Ankur Arora
2021-02-03 20:55 ` Laszlo Ersek
2021-02-04 2:57 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 8/9] OvmfPkg/CpuHotplugSmm: add worker to do CPU ejection Ankur Arora
2021-02-01 17:22 ` Laszlo Ersek
2021-02-01 19:21 ` Ankur Arora
2021-02-02 13:23 ` Laszlo Ersek
2021-02-03 5:41 ` Ankur Arora
2021-01-29 0:59 ` [PATCH v6 9/9] OvmfPkg/SmmControl2Dxe: negotiate CPU hot-unplug Ankur Arora
2021-02-01 17:37 ` Laszlo Ersek
2021-02-01 17:40 ` Laszlo Ersek
2021-02-01 17:48 ` Laszlo Ersek
2021-02-03 5:46 ` Ankur Arora
2021-02-03 20:45 ` Laszlo Ersek
2021-02-04 3:04 ` Ankur Arora [this message]
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