From: David Woodhouse <dwmw2@infradead.org>
To: Usama Arif <usama.arif@bytedance.com>,
Thomas Gleixner <tglx@linutronix.de>,
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
Subject: Re: [External] Re: [PATCH v8 8/9] x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup
Date: Thu, 09 Feb 2023 20:37:13 +0000 [thread overview]
Message-ID: <704abe334aa3166b579e1ba00369c977b1ea4d24.camel@infradead.org> (raw)
In-Reply-To: <9b6bca9c-7189-a2d5-8c0a-f55c24f54b62@bytedance.com>
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On Thu, 2023-02-09 at 20:32 +0000, Usama Arif wrote:
>
> I will let David confirm if this is correct and why he did it, but this
> is what I thought while reviewing before posting v4:
>
> - At initial boot (system_state < SYSTEM_RUNNING), when mtrr_save_state
> is called in do_cpu_up at roughly the same time so MTRR is going to be
> the same, we can just save it once and then reuse for other secondary
> cores as it wouldn't have changed for the rest of the do_cpu_up calls.
>
> - When the system is running and you offline and then online a CPU, you
> want to make sure that hotplugged CPU gets the current MTRR (which might
> have changed since boot?), incase the MTRR has changed after the system
> has been booted, you save the MTRR of the first online CPU. When the
> hotplugged CPU runs its initialisation code, its fixed-range MTRRs will
> be updated with the newly saved fixed-range MTRRs.
>
> So mainly for hotplug, but will let David confirm.
Sounds about right.
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next prev parent reply other threads:[~2023-02-09 20:37 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 15:41 [PATCH v8 0/9] Parallel CPU bringup for x86_64 Usama Arif
2023-02-09 15:41 ` [PATCH v8 1/9] x86/apic/x2apic: Allow CPU cluster_mask to be populated in parallel Usama Arif
2023-02-09 15:41 ` [PATCH v8 2/9] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-02-09 15:41 ` [PATCH v8 3/9] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-02-09 15:41 ` [PATCH v8 4/9] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() Usama Arif
2023-02-09 15:41 ` [PATCH v8 5/9] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-02-09 15:41 ` [PATCH v8 6/9] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-02-09 18:25 ` Thomas Gleixner
2023-02-09 20:37 ` [External] " Usama Arif
2023-02-09 15:41 ` [PATCH v8 7/9] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-02-09 15:41 ` [PATCH v8 8/9] x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup Usama Arif
2023-02-09 18:31 ` Thomas Gleixner
2023-02-09 20:32 ` [External] " Usama Arif
2023-02-09 20:37 ` David Woodhouse [this message]
2023-02-09 23:50 ` Thomas Gleixner
2023-02-10 8:55 ` David Woodhouse
2023-02-13 15:19 ` Usama Arif
2023-02-13 20:42 ` Thomas Gleixner
2023-02-09 15:41 ` [PATCH v8 9/9] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-02-13 20:43 ` Thomas Gleixner
2023-02-13 20:53 ` David Woodhouse
2023-02-13 22:30 ` [External] " Usama Arif
2023-02-14 6:57 ` David Woodhouse
2023-02-10 4:11 ` [PATCH v8 0/9] Parallel CPU bringup for x86_64 Paul E. McKenney
2023-02-10 9:02 ` David Woodhouse
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