linux-kernel - Re: [patch v3 31/36] x86/apic: Provide cpu_primary

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Date:   Mon, 29 May 2023 05:39:39 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Brian Gerst <brgerst@...il.com>,
        Arjan van de Veen <arjan@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul McKenney <paulmck@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Piotr Gorski <lucjan.lucjanov@...il.com>,
        Usama Arif <usama.arif@...edance.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        linux-csky@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Sabin Rapan <sabrapan@...zon.com>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [patch v3 31/36] x86/apic: Provide cpu_primary_thread mask

On Sat, May 27, 2023 at 03:40:02PM +0200, Thomas Gleixner wrote:
> On Fri, May 26 2023 at 12:14, Thomas Gleixner wrote:
> > On Wed, May 24 2023 at 23:48, Kirill A. Shutemov wrote:
> >> This patch causes boot regression on TDX guest. The guest crashes on SMP
> >> bring up.
> 
> The below should fix that. Sigh...

Okay, this gets me fixes the boot for TDX guest:

Tested-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

But it gets broken again on "x86/smpboot: Implement a bit spinlock to
protect the realmode stack" with

[    0.554079] .... node  #0, CPUs:        #1  #2
[    0.738071] Callback from call_rcu_tasks() invoked.
[   10.562065] CPU2 failed to report alive state
[   10.566337]   #3
[   20.570066] CPU3 failed to report alive state
[   20.574268]   #4
...

Notably CPU1 is missing from "failed to report" list. So CPU1 takes the
lock fine, but seems never unlocks it.

Maybe trampoline_lock(%rip) in head_64.S somehow is not the same as
&tr_lock in trampoline_64.S. I donno.

I haven't find the root cause yet. But bypassing locking in
LOAD_REALMODE_ESP makes the issue go away.

I will look more into it.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov