Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64
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>
References: <20211215145633.5238-1-dwmw2@infradead.org>
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 <721484e0fa719e99f9b8f13e67de05033dd7cc86.camel@infradead.org>
 <20211217110906.5c38fe7b@redhat.com>
 <d4cde50b4aab24612823714dfcbe69bc4bb63b60.camel@infradead.org>
 <36cc857b-7331-8305-ee25-55f6ba733ca6@amd.com>
 <c1726334d337de7d7a8361be27218b44784887f6.camel@infradead.org>
 <02be2ef0-8a18-553f-2bd7-1754c3f53477@amd.com>
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Date:   Tue, 21 Dec 2021 16:25:35 -0600
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On 12/20/21 3:47 PM, Tom Lendacky wrote:
> On 12/20/21 3:29 PM, David Woodhouse wrote:
>> On Mon, 2021-12-20 at 12:54 -0600, Tom Lendacky wrote:
>>> Took the tree back to commit df9726cb7178 and then applied this change.
>>> I'm unable to trigger any kind of failure with this change.
>>
>> Hm... I fired up an EC2 m6a.48xlarge instance (192 CPUs) to play with.
>>
>> I can reproduce your triple-fault on SMP bringup, but only with kexec.
>> And I basically can't get *anything* to kexec without that triple-
>> fault. Not a clean 5.16-rc2, not the Fedora stock 5.14.10 kernel.
>>
>> If I *boot* instead of kexec, I have not yet seen the problem at all.
>> This is using Legacy BIOS not UEFI.
> 
> Let me try with a legacy BIOS and see if I can repro. Might not be until 
> tomorrow, though, since I had to let someone borrow the machine.

I still encounter the issue using a legacy BIOS (SeaBIOS).

Thanks,
Tom

> 
> Thanks,
> Tom
> 
>>
>>