From: "Paul E. McKenney" <paulmck@kernel.org>
To: Usama Arif <usama.arif@bytedance.com>
Cc: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com,
arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org,
pbonzini@redhat.com, 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: [PATCH v7 0/9] Parallel CPU bringup for x86_64
Date: Wed, 8 Feb 2023 19:53:00 -0800 [thread overview]
Message-ID: <20230209035300.GA3216394@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20230207230436.2690891-1-usama.arif@bytedance.com>
On Tue, Feb 07, 2023 at 11:04:27PM +0000, Usama Arif wrote:
> Tested on v7, doing INIT/SIPI/SIPI in parallel brings down the time for
> smpboot from ~700ms to 100ms (85% improvement) on a server with 128 CPUs
> split across 2 NUMA nodes.
>
> The major change over v6 is keeping parallel smp support enabled in AMD.
> APIC ID for parallel CPU bringup is now obtained from CPUID leaf 0x0B
> (for x2APIC mode) otherwise CPUID leaf 0x1 (8 bits).
>
> The patch for reusing timer calibration for secondary CPUs is also removed
> from the series as its not part of parallel smp bringup and needs to be
> further thought about.
Running rcutorture on this got me the following NULL pointer dereference
on scenario TREE01:
------------------------------------------------------------------------
[ 34.662066] smpboot: CPU 0 is now offline
[ 34.674075] rcu: NOCB: Cannot CB-offload offline CPU 25
[ 35.038003] rcu: De-offloading 5
[ 35.112997] rcu: Offloading 12
[ 35.716011] smpboot: Booting Node 0 Processor 0 APIC 0x0
[ 35.762685] BUG: kernel NULL pointer dereference, address: 0000000000000001
[ 35.764278] #PF: supervisor instruction fetch in kernel mode
[ 35.765530] #PF: error_code(0x0010) - not-present page
[ 35.766700] PGD 0 P4D 0
[ 35.767278] Oops: 0010 [#1] PREEMPT SMP PTI
[ 35.768223] CPU: 36 PID: 0 Comm: swapper/36 Not tainted 6.2.0-rc1-00206-g18a37610b632-dirty #3563
[ 35.770201] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
------------------------------------------------------------------------
Given an x86 system with KVM and qemu, this can be reproduced by running
the following from the top-level directory in the Linux-kernel source
tree:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --configs "TREE01 TINY01" --trust-make
Out of 15 runs, 14 blew up just after the first attempt to bring CPU
0 back online. The 15th run blew up just after the second attempt to
bring CPU 0 online, the first attempt having succeeded.
My guess is that the CONFIG_BOOTPARAM_HOTPLUG_CPU0=y Kconfig option is
tickling this bug. This Kconfig option has been added to the TREE01
scenario in the -rcu tree's "dev" branch, which might mean that this test
would pass on mainline. But CONFIG_BOOTPARAM_HOTPLUG_CPU0=y is not new,
only rcutorture's testing of it.
Thoughts?
Thanx, Paul
next prev parent reply other threads:[~2023-02-09 3:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-07 23:04 [PATCH v7 0/9] Parallel CPU bringup for x86_64 Usama Arif
2023-02-07 23:04 ` [PATCH v7 1/9] x86/apic/x2apic: Allow CPU cluster_mask to be populated in parallel Usama Arif
2023-02-07 23:04 ` [PATCH v7 2/9] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-02-07 23:04 ` [PATCH v7 3/9] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-02-07 23:04 ` [PATCH v7 4/9] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() Usama Arif
2023-02-07 23:04 ` [PATCH v7 5/9] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-02-08 10:03 ` Yuan Yao
2023-02-08 12:02 ` David Woodhouse
2023-02-09 3:06 ` Yuan Yao
2023-02-07 23:04 ` [PATCH v7 6/9] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-02-08 5:09 ` Brian Gerst
2023-02-08 12:54 ` [External] " Usama Arif
2023-02-08 12:56 ` David Woodhouse
2023-02-08 13:13 ` Thomas Gleixner
2023-02-08 14:41 ` David Woodhouse
2023-02-07 23:04 ` [PATCH v7 7/9] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-02-07 23:04 ` [PATCH v7 8/9] x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup Usama Arif
2023-02-07 23:04 ` [PATCH v7 9/9] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-02-09 3:53 ` Paul E. McKenney [this message]
2023-02-09 9:49 ` [External] Re: [PATCH v7 0/9] Parallel CPU bringup for x86_64 Usama Arif
2023-02-09 10:06 ` David Woodhouse
2023-02-09 10:19 ` Usama Arif
2023-02-09 10:22 ` David Woodhouse
2023-02-09 11:03 ` David Woodhouse
2023-02-09 11:45 ` Usama Arif
2023-02-09 11:53 ` Thomas Gleixner
2023-02-09 12:10 ` David Woodhouse
2023-02-09 13:48 ` David Woodhouse
2023-02-09 14:01 ` Usama Arif
2023-02-09 15:48 ` Thomas Gleixner
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