linux-kernel - Re: [External] Re: [PATCH v9 0/8] Parallel CPU bringup for x86

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Date:   Mon, 20 Feb 2023 22:23:43 +0000
From:   Usama Arif <usama.arif@...edance.com>
To:     Oleksandr Natalenko <oleksandr@...alenko.name>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     tglx@...utronix.de, kim.phillips@....com, arjan@...ux.intel.com,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, x86@...nel.org, pbonzini@...hat.com,
        paulmck@...nel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, rcu@...r.kernel.org, mimoja@...oja.de,
        hewenliang4@...wei.com, thomas.lendacky@....com, seanjc@...gle.com,
        pmenzel@...gen.mpg.de, fam.zheng@...edance.com,
        punit.agrawal@...edance.com, simon.evans@...edance.com,
        liangma@...ngbit.com, Piotr Gorski <lucjan.lucjanov@...il.com>
Subject: Re: [External] Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64



On 20/02/2023 21:23, Oleksandr Natalenko wrote:
> Hello.
> 
> On 20.02.2023 21:31, David Woodhouse wrote:
>> On Mon, 2023-02-20 at 17:40 +0100, Oleksandr Natalenko wrote:
>>> On pondělí 20. února 2023 17:20:13 CET David Woodhouse wrote:
>>> > On Mon, 2023-02-20 at 17:08 +0100, Oleksandr Natalenko wrote:
>>> > >
>>> > > I've applied this to the v6.2 kernel, and suspend/resume broke on
>>> > > my
>>> > > Ryzen 5950X desktop. The machine suspends just fine, but on
>>> > > resume
>>> > > the screen stays blank, and there's no visible disk I/O.
>>> > >
>>> > > Reverting the series brings suspend/resume back to working state.
>>> >
>>> > Hm, thanks. What if you add 'no_parallel_bringup' on the command
>>> > line?
>>>
>>> If the `no_parallel_bringup` param is added, the suspend/resume
>>> works.
>>
>> Thanks for the testing. Can I ask you to do one further test: apply the
>> series only as far as patch 6/8 'x86/smpboot: Support parallel startup
>> of secondary CPUs'.
>>
>> That will do the new startup asm sequence where each CPU finds its own
>> per-cpu data so it *could* work in parallel, but doesn't actually do
>> the bringup in parallel yet.
> 
> With patches 1 to 6 (including) applied and no extra cmdline params 
> added the resume doesn't work.
> 
>> Does your box have a proper serial port?
> 
> No, sorry. I know it'd help with getting logs, and I do have a 
> serial-to-USB cable that I use for another machine, but in this one the 
> port is not routed to outside. I think I can put a header there as the 
> motherboard does have pins, but I'd have to buy one first. In theory, I 
> can do that, but that won't happen within the next few weeks.
> 
> P.S. Piotr Gorski (in Cc) also reported this: "My friend from CachyOS 
> can confirm bugs with smpboot patches. AMD FX 6300 only shows 1 core 
> when using smp boot patchset". Probably, he can reply to this thread and 
> provide more details.
> 

Hi Oleksandr,

So for initial boot, do all CPUs comes up for you when parallel smp boot 
is enabled or only 1?

I don't have access to Ryzen hardware so can only say from code, but it 
would be weird if initial boot is fine but resume is broken if the same 
code path is being taken.

Thanks,
Usama