linux-kernel - Re: [PATCH v4 2/4] x86/boot: Add acpitb.c to parse acpi tables

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Message-ID: <20180803020844.GF6723@localhost.localdomain>
Date:   Fri, 3 Aug 2018 10:08:45 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <hpa@...or.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bhe@...hat.com>,
        <keescook@...omium.org>, <yasu.isimatu@...il.com>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>,
        <fanc.fnst@...fujitsu.com>
Subject: Re: [PATCH v4 2/4] x86/boot: Add acpitb.c to parse acpi tables

On Fri, Aug 03, 2018 at 10:00:48AM +0800, Dou Liyang wrote:
>
>
>At 07/23/2018 05:29 PM, Chao Fan wrote:
>> Imitate the ACPI code to parse ACPI tables. Functions are simplified
>> cause some operations are not needed here.
>> And also, this method won't influence the initialization of ACPI.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
>
>Hi Fan,
>
>I know you got the code from acpica subsystem and EFI code... and do
>many adaptation work for KASLR. It's awesome!
>
>I think you can add some other simple comments.
>
>  - what differences between your function and the function you based on
>    and why did you do that?
>
>... to make this more credible and easy to remember the details as time
>goes on.

That's a good idea, will add more comments.

>
>Also some concerns below.
>> ---
>[...]
>> +	else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4))
>> +		efi_64 = false;
>> +	else {
>> +		debug_putstr("Wrong efi loader signature.\n");
>
>s/efi/EFI/, also need fix in the comments below.
>
>> +		return false;
>> +	}
>> +
>[...]
>> +		/*
>> +		 * Get rsdp from efi tables.
>> +		 * If we find acpi table, go on searching for acpi20 table.
>> +		 * If we didn't get acpi20 table then use acpi table.
>> +		 * If neither acpi table nor acpi20 table found,
>> +		 * return false.
>> +		 */
>> +		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)) && !acpi_20) {
>> +			*rsdp_addr = (acpi_physical_address)table;
>> +			acpi_20 = false;
>> +			find_rsdp = true;
>> +		} else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID))) {
>> +			*rsdp_addr = (acpi_physical_address)table;
>> +			acpi_20 = true;
>> +			return true;
>
>If we find the ACPI 2.0, we will return immediately, so the variable and
>logic of _acpi_20_ is redundant.

I will check the logical and fix the mistake.

Thanks,
Chao Fan

>
>Thanks,
>	dou