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From: Thomas Gleixner <tglx@linutronix.de>
To: David Woodhouse <dwmw2@infradead.org>,
	Usama Arif <usama.arif@bytedance.com>,
	kim.phillips@amd.com
Cc: arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de,
	dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org,
	pbonzini@redhat.com, paulmck@kernel.org,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com,
	thomas.lendacky@amd.com, seanjc@google.com,
	pmenzel@molgen.mpg.de, fam.zheng@bytedance.com,
	punit.agrawal@bytedance.com, simon.evans@bytedance.com,
	liangma@liangbit.com, Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64
Date: Thu, 23 Feb 2023 15:37:02 +0100	[thread overview]
Message-ID: <87zg94la7l.ffs@tglx> (raw)
In-Reply-To: <701ce2da00e559d517d4e48bd5d88ccae1198e44.camel@infradead.org>

David!

On Thu, Feb 23 2023 at 11:07, David Woodhouse wrote:
> On Wed, 2023-02-22 at 17:42 +0100, Thomas Gleixner wrote:
>> The low hanging fruit which brings most is the identification/topology
>> muck and the microcode loading. That needs to be addressed first anyway.
>
> Agreed, thanks.

So the problem with microcode loading is that we must ensure that a HT
sibling is not executing anything else than a trivial loop waiting for
the update to complete. So something like this should work:

   1) Kick all CPUs into life and let them run up to cpu_init() and
      retrieve only the topology information.

   2) Wait for all CPUs to reach this point

   3) Release all primary HT threads so they can load microcode in
      parallel. The secondary HT threads stay in the wait loop and are
      released once the primary thread has finished the microcode
      update.

   4) Let the CPUs do the full CPUID readout and let them synchronize
      with the control CPU again.

   5) Complete bringup one by one

Thanks,

        tglx
      


   



  reply	other threads:[~2023-02-23 14:37 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-15 14:54 [PATCH v9 0/8] Parallel CPU bringup for x86_64 Usama Arif
2023-02-15 14:54 ` [PATCH v9 1/8] x86/apic/x2apic: Allow CPU cluster_mask to be populated in parallel Usama Arif
2023-02-16 20:58   ` Kim Phillips
2023-02-15 14:54 ` [PATCH v9 2/8] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-02-15 14:54 ` [PATCH v9 3/8] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-02-15 14:54 ` [PATCH v9 4/8] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() Usama Arif
2023-02-15 14:54 ` [PATCH v9 5/8] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-02-15 14:54 ` [PATCH v9 6/8] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-02-15 14:54 ` [PATCH v9 7/8] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-02-15 14:54 ` [PATCH v9 8/8] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-02-16  6:34 ` [PATCH v9 0/8] Parallel CPU bringup for x86_64 Paul E. McKenney
2023-02-20 16:08 ` Oleksandr Natalenko
2023-02-20 16:20   ` David Woodhouse
2023-02-20 16:40     ` Oleksandr Natalenko
2023-02-20 20:31       ` David Woodhouse
2023-02-20 21:23         ` Oleksandr Natalenko
2023-02-20 21:34           ` Piotr Gorski
2023-02-20 21:39           ` David Woodhouse
2023-02-20 23:23             ` Kim Phillips
2023-02-20 23:30               ` David Woodhouse
2023-02-21  4:20                 ` Kim Phillips
2023-02-21  7:16                   ` David Woodhouse
2023-02-21  7:27                 ` Oleksandr Natalenko
2023-02-21  7:53                   ` David Woodhouse
2023-02-21  8:05                     ` Oleksandr Natalenko
2023-02-21  8:17                       ` David Woodhouse
2023-02-21  8:25                         ` Oleksandr Natalenko
2023-02-21  8:35                           ` David Woodhouse
2023-02-21  8:44                             ` Oleksandr Natalenko
2023-02-21  9:06                               ` David Woodhouse
2023-02-21  9:49                                 ` Oleksandr Natalenko
2023-02-21 10:27                                   ` David Woodhouse
2023-02-21 10:47                                     ` [External] " Usama Arif
2023-02-21 11:42                                       ` Oleksandr Natalenko
2023-02-21 11:54                                         ` Usama Arif
2023-02-21 13:22                                           ` David Woodhouse
2023-02-21 11:46                                     ` Oleksandr Natalenko
2023-02-21 11:49                                       ` David Woodhouse
2023-02-21 12:14                                         ` Oleksandr Natalenko
2023-02-21 19:10                                           ` David Woodhouse
2023-02-21 20:04                                             ` [External] " Usama Arif
2023-02-21 21:04                                               ` Oleksandr Natalenko
2023-02-21 21:41                                             ` Thomas Gleixner
2023-02-21 21:44                                               ` David Woodhouse
2023-02-21 23:18                                               ` David Woodhouse
2023-02-22  0:00                                                 ` [External] " Usama Arif
2023-02-22  8:19                                                   ` David Woodhouse
2023-02-22  9:46                                                     ` Thomas Gleixner
2023-02-22  9:51                                                       ` David Woodhouse
2023-02-22  9:31                                                 ` Thomas Gleixner
2023-02-20 22:22           ` Piotr Gorski
2023-02-20 22:23           ` [External] " Usama Arif
2023-02-20 22:41             ` Oleksandr Natalenko
2023-02-22 10:11 ` David Woodhouse
2023-02-22 11:11   ` [External] " Usama Arif
2023-02-22 12:08   ` Brian Gerst
2023-02-22 12:53     ` David Woodhouse
2023-02-22 16:42   ` Thomas Gleixner
2023-02-23 11:07     ` David Woodhouse
2023-02-23 14:37       ` Thomas Gleixner [this message]
2023-02-23 15:12         ` David Woodhouse
2023-02-23 19:24       ` [External] " Usama Arif

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