linux-kernel - Re: [PATCH v3 0/9] Parallel CPU bringup for x86

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Message-ID: <c3dbd3b9-accf-bc28-f808-1d842d642309@amd.com>
Date:   Fri, 17 Dec 2021 14:55:02 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "rcu@...r.kernel.org" <rcu@...r.kernel.org>,
        "mimoja@...oja.de" <mimoja@...oja.de>,
        "hewenliang4@...wei.com" <hewenliang4@...wei.com>,
        "hushiyuan@...wei.com" <hushiyuan@...wei.com>,
        "luolongjun@...wei.com" <luolongjun@...wei.com>,
        "hejingxian@...wei.com" <hejingxian@...wei.com>
Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64

On 12/17/21 2:13 PM, David Woodhouse wrote:
> On Fri, 2021-12-17 at 13:46 -0600, Tom Lendacky wrote:
>> There's no WARN or PANIC, just a reset. I can look to try and capture some
>> KVM trace data if that would help. If so, let me know what events you'd
>> like captured.
> 
> 
> Could start with just kvm_run_exit?
> 
> Reason 8 would be KVM_EXIT_SHUTDOWN and would potentially indicate a
> triple fault.

qemu-system-x86-24093   [005] .....  1601.759486: kvm_exit: vcpu 112 reason shutdown rip 0xffffffff81070574 info1 0x0000000000000000 info2 0x0000000000000000 intr_info 0x80000b08 error_code 0x00000000

# addr2line -e woodhouse-build-x86_64/vmlinux 0xffffffff81070574
/root/kernels/woodhouse-build-x86_64/./arch/x86/include/asm/desc.h:272

Which is: asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));

Thanks,
Tom

> 
> Failing that, I'd want to start littering the real mode code with
> outputting 'a' 'b' 'c' etc. to the serial port and see if the offending
> CPU is really in the trampoline somewhere when something goes wrong.
> 
> I can knock up an example patch to do that (not tonight) but this would
> be somewhat easier if I could find a machine I can reproduce on. Sadly
> I only seem to have access to Milan *guests* without nested virt, not
> bare metal. Got a machine I can log in to?
> 
>   
>