linux-kernel - Re: [PATCH v2] x86/boot: Use EFI setup data if provided

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Date:   Fri, 29 Mar 2019 17:44:09 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
CC:     Borislav Petkov <bp@...en8.de>, "bhe@...hat.com" <bhe@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        "kasong@...hat.com" <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Use EFI setup data if provided

On Fri, Mar 29, 2019 at 09:37:00AM +0000, Junichi Nomura wrote:
>On 3/29/19 6:16 PM, Borislav Petkov wrote:
>> On Fri, Mar 29, 2019 at 05:05:50PM +0800, Chao Fan wrote:
>>> But in my code, I am not sure which version will be found firstly, so I
>>> write this logical, if ACPI20 found, return directly, then consider ACPI 1.0.
>> 
>> Thanks.
>> 
>> Junichi, please add a shorter version of that as a comment to the code,
>> above the function name so that it is clear why we're preferring the 2.0
>> version.
>
>Sure, I'll add this above __efi_get_rsdp_addr().
>
>/*
> * Search EFI system tables for RSDP.  If both ACPI_20_TABLE_GUID and
> * ACPI_TABLE_GUID are found, take the former, which has more features.
> */
>

I notice in my host machine, the two tables are the same:
[17:38:11] cfan@...alhost /home/cfan (0)
> sudo cat /sys/firmware/efi/systab
[sudo] password for cfan:
MPS=0xfd420
ACPI20=0xdb807000
ACPI=0xdb807000
SMBIOS=0xf04c0

But in my qemu guest, they are different and the address of ACPI20 is
higher than ACPI 1.0:
[root@...alhost ~]# cat /sys/firmware/efi/systab
ACPI20=0xbfbfa014
ACPI=0xbfbfa000
SMBIOS=0xbfbcc000

In this condition, ACPI 1.0 comes before ACPI 2.0. So I suggested you
to keep this logical.

Thanks,
Chao Fan

>-- 
>Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.
>