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

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Message-ID: <0263068e-f2d0-1101-0438-0f570f0b38e7@ce.jp.nec.com>
Date:   Fri, 29 Mar 2019 03:05:52 +0000
From:   Junichi Nomura <j-nomura@...jp.nec.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "bhe@...hat.com" <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.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 3/29/19 12:52 AM, Borislav Petkov wrote:
> static acpi_physical_address
> __efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
>                     int size, bool efi_64)
> 
> 
>>  {
>>  	acpi_physical_address rsdp_addr = 0;
> 
> You don't need that variable and can return "table" or 0 after the endif
> below.

I could do that but it will slightly change the current logic.

Existing code does this:

                if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
                        rsdp_addr = table;
                else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
                        return table;

I thought it was to return the table for ACPI_20_TABLE_GUID
if both tables exist.  If we remove rsdp_addr, the code will be:

                if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
                        return table;
                else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
                        return table;

So if there are 2 tables, we return the one that comes first.
Is it ok?

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