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

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Message-ID: <20230530005428.jyrc2ezx5raohlrt@box.shutemov.name>
Date:   Tue, 30 May 2023 03:54:28 +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 Mon, May 29, 2023 at 11:31:29PM +0300, Kirill A. Shutemov wrote:
> On Mon, May 29, 2023 at 09:27:13PM +0200, Thomas Gleixner wrote:
> > On Mon, May 29 2023 at 05:39, Kirill A. Shutemov wrote:
> > > On Sat, May 27, 2023 at 03:40:02PM +0200, Thomas Gleixner wrote:
> > > 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.
> > 
> > It's definitely the same in the regular startup (16bit mode), but TDX
> > starts up via:
> > 
> > trampoline_start64
> >   trampoline_compat
> >     LOAD_REALMODE_ESP <- lock
> > 
> > That place cannot work with that LOAD_REALMODE_ESP macro. The untested
> > below should cure it.
> 
> Yep, works for me.
> 
> Aaand the next patch that breaks TDX boot is... <drum roll>
> 
> 	x86/smpboot/64: Implement arch_cpuhp_init_parallel_bringup() and enable it
> 
> Disabling parallel bringup helps. I didn't look closer yet. If you have
> an idea let me know.

Okay, it crashes around .Lread_apicid due to touching MSRs that trigger #VE.

Looks like the patch had no intention to enable parallel bringup on TDX.

+        * Intel-TDX has a secure RDMSR hypercall, but that needs to be
+        * implemented seperately in the low level startup ASM code.

But CC_ATTR_GUEST_STATE_ENCRYPT that used to filter it out is
SEV-ES-specific thingy and doesn't cover TDX. I don't think we have an
attribute that fits nicely here.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov