linux-kernel - Re: [PATCHv2 13/13] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method

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Date:   Fri, 27 Oct 2023 14:58:13 +0300
From:   "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "ashish.kalra@....com" <ashish.kalra@....com>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>
Subject: Re: [PATCHv2 13/13] x86/acpi: Add support for CPU offlining for ACPI
 MADT wakeup method

On Tue, Oct 24, 2023 at 10:11:58AM +0000, Huang, Kai wrote:
> 
> > --- /dev/null
> > +++ b/arch/x86/kernel/acpi/madt.S
> 
> I think the name 'madt.S' is too generic.  How about something be more specific
> such as madt_reset.S, or madt_playdead.S, etc? 

Okay, madt_playdead.S sounds good.

> > @@ -11,6 +16,150 @@ static u64 acpi_mp_wake_mailbox_paddr;
> >  /* Virtual address of the Multiprocessor Wakeup Structure mailbox */
> >  static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
> >  
> > +u64 acpi_mp_pgd;
> > +u64 acpi_mp_reset_vector_paddr;
> > +
> > +void asm_acpi_mp_play_dead(void);
> > +
> > +static void __init *alloc_pgt_page(void *context)
> > +{
> > +	return memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> > +}
> > +
> > +/*
> > + * Make sure asm_acpi_mp_play_dead() is present in the identity mapping at
> > + * the same place as in the kernel page tables. The function switches to
> > + * the identity mapping 
> > 
> 
> This function itself doesn't switch to the identity mapping.  It just creates
> the kernel mapping for asm_acpi_mp_play_dead() in the identify mapping page
> table.

By "The function" I meant asm_acpi_mp_play_dead(). Yeah, it is not clear.

Will so s/The function/asm_acpi_mp_play_dead()/

> > -	cpu_hotplug_disable_offlining();
> > +	if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
> > +	    mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
> > +		acpi_mp_setup_reset(mp_wake->reset_vector);
> 
> It's better to fallback to "disable offline" if this function fails.
> 

Okay, will warn to disable offlining.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov