From: Tom Lendacky <thomas.lendacky@amd.com>
To: David Woodhouse <dwmw2@infradead.org>,
Igor Mammedov <imammedo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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>
Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64
Date: Mon, 20 Dec 2021 12:54:12 -0600 [thread overview]
Message-ID: <36cc857b-7331-8305-ee25-55f6ba733ca6@amd.com> (raw)
In-Reply-To: <d4cde50b4aab24612823714dfcbe69bc4bb63b60.camel@infradead.org>
On 12/20/21 11:10 AM, David Woodhouse wrote:
> On Fri, 2021-12-17 at 11:09 +0100, Igor Mammedov wrote:
>> On Fri, 17 Dec 2021 00:13:16 +0000
>> David Woodhouse <dwmw2@infradead.org> wrote:
>>
>>> On Thu, 2021-12-16 at 16:52 -0600, Tom Lendacky wrote:
>>>> On baremetal, I haven't seen an issue. This only seems to have a problem
>>>> with Qemu/KVM.
>>>>
>>>> With 191f08997577 I could boot without issues with and without the
>>>> no_parallel_bringup. Only after I applied e78fa57dd642 did the failure happen.
>>>>
>>>> With e78fa57dd642 I could boot 64 vCPUs pretty consistently, but when I
>>>> jumped to 128 vCPUs it failed again. When I moved the series to
>>>> df9726cb7178, then 64 vCPUs also failed pretty consistently.
>>>>
>>>> Strange thing is it is random. Sometimes (rarely) it works on the first
>>>> boot and then sometimes it doesn't, at which point it will reset and
>>>> reboot 3 or 4 times and then make it past the failure and fully boot.
>>>
>>> Hm, some of that is just artifacts of timing, I'm sure. But now I'm
>>
>> that's most likely the case (there is a race somewhere left).
>> To trigger CPU bringup (hotplug) races, I used to run QEMU guest with
>> heavy vCPU overcommit. It helps to induce unexpected delays at CPU bringup
>> time.
>
> That last commit which actually enables parallel bringup does *two*
> things. It makes the generic cpuhp code bring all the CPUs through all
> the CPUHP_*_PREPARE stages and then actually brings them up. With that
> test patch I sent, the bringup basically *wasn't* parallel any more;
> they were using the trampoline lock all the way to the point where they
> start waiting on cpu_callin_mask.
>
> So maybe it's the 'prepare' ordering, like the x2apic one I already
> fixed... but some weirdness that only triggers on some CPUs. Can we
> back out the actual pseudo-parallel bringup and do *only* the prepare
> part, by doing something like this on top...
>
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1337,7 +1337,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
> int ret;
>
> /* If parallel AP bringup isn't enabled, perform the first steps now. */
> - if (!do_parallel_bringup) {
> + if (1 || !do_parallel_bringup) {
> ret = do_cpu_up(cpu, tidle);
> if (ret)
> return ret;
> @@ -1366,7 +1366,8 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
> /* Bringup step one: Send INIT/SIPI to the target AP */
> static int native_cpu_kick(unsigned int cpu)
> {
> - return do_cpu_up(cpu, idle_thread_get(cpu));
> + return 0;
> + // return do_cpu_up(cpu, idle_thread_get(cpu));
> }
Took the tree back to commit df9726cb7178 and then applied this change.
I'm unable to trigger any kind of failure with this change.
Thanks,
Tom
>
> /**
>
>
next prev parent reply other threads:[~2021-12-20 18:54 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=36cc857b-7331-8305-ee25-55f6ba733ca6@amd.com \
--to=thomas.lendacky@amd.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=dwmw2@infradead.org \
--cc=hejingxian@huawei.com \
--cc=hewenliang4@huawei.com \
--cc=hpa@zytor.com \
--cc=hushiyuan@huawei.com \
--cc=imammedo@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luolongjun@huawei.com \
--cc=mimoja@mimoja.de \
--cc=mingo@redhat.com \
--cc=paulmck@kernel.org \
--cc=pbonzini@redhat.com \
--cc=rcu@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).