linux-kernel - Re: [PATCHv8 17/17] ACPI: tables: Print MULTIPROC

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Message-ID: <3jgmzzbjmwtf2rtrbiulhwjj5xwzc3icf4gxcmugyyq5n7pg5m@ua3poay4gmku>
Date: Wed, 28 Feb 2024 17:22:30 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: "Huang, Kai" <kai.huang@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, Elena Reshetova <elena.reshetova@...el.com>, 
	Jun Nakajima <jun.nakajima@...el.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Tom Lendacky <thomas.lendacky@....com>, "Kalra, Ashish" <ashish.kalra@....com>, 
	Sean Christopherson <seanjc@...gle.com>, Baoquan He <bhe@...hat.com>, kexec@...ts.infradead.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv8 17/17] ACPI: tables: Print MULTIPROC_WAKEUP when MADT
 is parsed

On Wed, Feb 28, 2024 at 11:08:38AM +1300, Huang, Kai wrote:
> 
> 
> On 28/02/2024 10:24 am, Kirill A. Shutemov wrote:
> > When MADT is parsed, print MULTIPROC_WAKEUP information:
> > 
> > ACPI: MP Wakeup (version[1], mailbox[0x7fffd000], reset[0x7fffe068])
> > 
> > This debug information will be very helpful during bring up.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Reviewed-by: Baoquan He <bhe@...hat.com>
> > ---
> >   drivers/acpi/tables.c | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
> > index b07f7d091d13..c59a3617bca7 100644
> > --- a/drivers/acpi/tables.c
> > +++ b/drivers/acpi/tables.c
> > @@ -198,6 +198,20 @@ void acpi_table_print_madt_entry(struct acpi_subtable_header *header)
> >   		}
> >   		break;
> > +	case ACPI_MADT_TYPE_MULTIPROC_WAKEUP:
> > +		{
> > +			struct acpi_madt_multiproc_wakeup *p =
> > +				(struct acpi_madt_multiproc_wakeup *)header;
> > +			u64 reset_vector = 0;
> > +
> > +			if (p->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1)
> > +				reset_vector = p->reset_vector;
> > +
> > +			pr_debug("MP Wakeup (version[%d], mailbox[%#llx], reset[%#llx])\n",
> > +				 p->version, p->mailbox_address, reset_vector);
> > +		}
> > +		break;
> > +
> 
> Hmm.. I hate to say, but maybe it is better to put this patch at some early
> place in this series w/o mailbox version and reset_vector, and add
> incremental changes where mailbox/reset_vector is introduced in this series.
> 
> The advantage is in this way someone can just backport this patch to the old
> kernel if they care -- this should be part of commit f39642d0dbacd
> ("x86/acpi/x86/boot: Add multiprocessor wake-up support") anyway.

It is not subject for backporting. It is just a cosmetics fix (or debug
facility). Any new MADT type would generate a warning. Nothing wrong with
it.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov