linux-kernel - Re: [PATCH v2 2/2] x86/acpi: Remove the repeated lapic address override entry parsing

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Date:	Sat, 9 Jul 2016 10:04:21 +0800
From:	Baoquan He <bhe@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>, linux-acpi@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...nel.org>, Shaohua Li <shli@...com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Juergen Gross <jgross@...e.com>,
	Joerg Roedel <jroedel@...e.de>, Dave Young <dyoung@...hat.com>,
	Lv Zheng <lv.zheng@...el.com>, Toshi Kani <toshi.kani@....com>,
	Mark Salter <msalter@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Subject: Re: [PATCH v2 2/2] x86/acpi: Remove the repeated lapic address
 override entry parsing

Hi Ingo,

On 07/08/16 at 02:27pm, Ingo Molnar wrote:
> 
> * Baoquan He <bhe@...hat.com> wrote:
> 
> > ACPI MADT has a 32-bit field providing lapic address at which
> > each processor can access its lapic information. MADT also contains
> > an optional entry to provide a 64-bit address to override the 32-bit
> > one. However the current code does the lapic address override entry
> > parsing twice. One is in early_acpi_boot_init() because AMD NUMA need
> > get boot_cpu_id earlier. The other is in acpi_boot_init() which parses
> > all MADT entries.
> > 
> > So in this patch remove the repeated code in the 2nd part. Meanwhile
> > print lapic override entry information like other MADT entry.
> 
> So this patch is not supposed to change behavior (modulo kernel messages), right? 
> If so it would make sense to spell that out explicitly in the changelog.

I am not sure if I understand your question correctly. In this patch I
added the calling of acpi_table_print_madt_entry(header) in
acpi_parse_lapic_addr_ovr, it will print information related if a lapic
address override entry is provided as below:

	case ACPI_MADT_TYPE_LOCAL_APIC_OVERRIDE:                                                                  
                {                                                                                                 
                        struct acpi_madt_local_apic_override *p =                                                 
                            (struct acpi_madt_local_apic_override*)header;                                       
                        pr_info("LAPIC_ADDR_OVR (address[%p])\n",                                                 
                                (void *)(unsigned long)p->address);                                               
                }                                                                                                 
                break;

This will add one line of message to boot log if lapic addr override
entry provided:
"LAPIC_ADDR_OVR (address[0xXXXXXXXX])"

I don't know if this is the behaviour change (modulo kernel messages)
you mentioned.

Thanks
Baoquan