From: Borislav Petkov <bp@alien8.de>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Sean Christopherson <seanjc@google.com>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"rcu@vger.kernel.org" <rcu@vger.kernel.org>,
"mimoja@mimoja.de" <mimoja@mimoja.de>,
"hewenliang4@huawei.com" <hewenliang4@huawei.com>,
"hushiyuan@huawei.com" <hushiyuan@huawei.com>,
"luolongjun@huawei.com" <luolongjun@huawei.com>,
"hejingxian@huawei.com" <hejingxian@huawei.com>,
Joerg Roedel <joro@8bytes.org>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v3 6/9] x86/smpboot: Support parallel startup of secondary CPUs
Date: Tue, 1 Feb 2022 11:56:08 +0100 [thread overview]
Message-ID: <YfkRyLV/auNzczfF@zn.tnic> (raw)
In-Reply-To: <3bc401a9f110a24a429316371c767507b493025a.camel@infradead.org>
On Tue, Feb 01, 2022 at 10:25:01AM +0000, David Woodhouse wrote:
> Thanks. It looks like that is only invoked after boot, with a write to
> /sys/devices/system/cpu/microcode/reload.
>
> My series is only parallelising the initial bringup at boot time, so it
> shouldn't make any difference.
No, I don't mean __reload_late() - I pointed you at that function to
show the dance we must do when updating microcode late.
The load_ucode_{ap,bsp}() routines are what is called when loading ucode
early.
So the question is, does the parallelizing change the order in which APs
are brought up and can it happen that a SMT sibling of a two-SMT core
executes *something* while the other SMT sibling is updating microcode.
If so, that would be bad.
> However... it does look like there's nothing preventing a sibling being
> brought online *while* the dance you mention above is occurring.
Bottom line is: of the two SMT siblings, one needs to be updating
microcode while the other is idle. I.e., what __reload_late() does.
> Shouldn't __reload_late() take the device_hotplug_lock to prevent that?
See reload_store().
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2022-02-01 10:56 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-15 14:56 [PATCH v3 0/9] Parallel CPU bringup for x86_64 David Woodhouse
2021-12-15 14:56 ` [PATCH v3 1/9] x86/apic/x2apic: Fix parallel handling of cluster_mask David Woodhouse
2021-12-15 14:56 ` [PATCH v3 2/9] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> David Woodhouse
2021-12-15 14:56 ` [PATCH v3 3/9] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU David Woodhouse
2021-12-15 14:56 ` [PATCH v3 4/9] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() David Woodhouse
2021-12-15 14:56 ` [PATCH v3 5/9] x86/smpboot: Split up native_cpu_up into separate phases and document them David Woodhouse
2021-12-15 14:56 ` [PATCH v3 6/9] x86/smpboot: Support parallel startup of secondary CPUs David Woodhouse
2021-12-16 14:24 ` Tom Lendacky
2021-12-16 18:24 ` David Woodhouse
2021-12-16 19:00 ` Tom Lendacky
2021-12-16 19:20 ` David Woodhouse
2022-01-29 12:04 ` David Woodhouse
2022-01-31 13:59 ` Borislav Petkov
2022-02-01 10:25 ` David Woodhouse
2022-02-01 10:56 ` Borislav Petkov [this message]
2022-02-01 12:39 ` David Woodhouse
2022-02-01 12:56 ` Borislav Petkov
2022-02-01 13:02 ` David Woodhouse
2021-12-15 14:56 ` [PATCH v3 7/9] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel David Woodhouse
2021-12-15 14:56 ` [PATCH v3 8/9] x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup David Woodhouse
2021-12-15 14:56 ` [PATCH v3 9/9] x86/smpboot: Serialize topology updates for secondary bringup David Woodhouse
2021-12-16 16:27 ` [PATCH v3 0/9] Parallel CPU bringup for x86_64 Tom Lendacky
2021-12-16 19:24 ` David Woodhouse
2021-12-16 22:52 ` Tom Lendacky
2021-12-17 0:13 ` David Woodhouse
2021-12-17 10:09 ` Igor Mammedov
2021-12-17 15:40 ` David Woodhouse
2021-12-20 17:10 ` David Woodhouse
2021-12-20 18:54 ` Tom Lendacky
2021-12-20 21:29 ` David Woodhouse
2021-12-20 21:47 ` Tom Lendacky
2021-12-21 22:25 ` Tom Lendacky
2021-12-21 22:33 ` David Woodhouse
2021-12-17 17:48 ` Tom Lendacky
2021-12-17 19:11 ` David Woodhouse
2021-12-17 19:26 ` David Woodhouse
2021-12-17 20:15 ` Tom Lendacky
2021-12-17 19:46 ` Tom Lendacky
2021-12-17 20:13 ` David Woodhouse
2021-12-17 20:55 ` Tom Lendacky
2021-12-17 22:48 ` David Woodhouse
2022-01-28 9:54 ` David Woodhouse
2022-01-28 21:40 ` Sean Christopherson
2022-01-28 21:48 ` David Woodhouse
2022-01-29 9:22 ` David Woodhouse
2021-12-16 19:52 ` David Woodhouse
2021-12-16 19:55 ` Tom Lendacky
2021-12-16 19:59 ` David Woodhouse
2021-12-27 16:57 ` Paul Menzel
2021-12-28 11:34 ` Paul Menzel
2021-12-28 14:18 ` David Woodhouse
2021-12-29 13:18 ` Paul Menzel
2021-12-29 13:54 ` David Woodhouse
2022-02-14 13:45 ` Paul Menzel
2022-04-21 10:00 ` Mimoja
2022-04-22 21:19 ` Tom Lendacky
2022-06-01 8:30 ` David Woodhouse
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