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

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Date:   Fri, 29 Mar 2019 09:39:20 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Junichi Nomura <j-nomura@...jp.nec.com>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>
Cc:     "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 03:05:52AM +0000, Junichi Nomura wrote:
> > 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?

That's a good question.

Chao, what was the intention there, ACPI_20_TABLE_GUID is the preferred
table to return? If so, why?

-- 
Regards/Gruss,
    Boris.

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