linux-kernel - Re: [PATCH 2/2] arm64: acpi: Prepare for longer MADTs

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Date:   Tue, 27 Nov 2018 10:32:37 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
        will.deacon@....com, ard.biesheuvel@...aro.org,
        james.morse@....com, rafael.j.wysocki@...el.com,
        takahiro.akashi@...aro.org, sudeep.holla@....com, ahs3@...hat.com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: acpi: Prepare for longer MADTs

Hi Lorenzo,

On 11/27/2018 09:01 AM, Lorenzo Pieralisi wrote:
> On Fri, Oct 12, 2018 at 02:29:37PM -0500, Jeremy Linton wrote:
>> The BAD_MADT_GICC_ENTRY check is a little too strict because
>> it rejects MADT entries that don't match the currently known
>> lengths. We should remove this restriction to avoid problems
>> if the table length changes. Future code which might depend on
>> additional fields should be written to validate those fields
>> before using them, rather than trying to globally check
>> known MADT version lengths.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>> ---
>>   arch/arm64/include/asm/acpi.h | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> Hi Jeremy,
> 
> as mentioned, I added a comment to the macro so that in the future
> we will be able to remember the logic behind it.

It all looks good to me, Thanks!


> 
> I pushed the commit out:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/linux.git acpi/madt
> 
> Please have a look, if I hear no objections I shall be sending it to
> Will and Catalin to queue it for v4.21.
> 
> Thanks,
> Lorenzo
> 
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index 709208dfdc8b..4d0946bd485a 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -22,12 +22,12 @@
>>   #include <asm/tlbflush.h>
>>   
>>   /* Macros for consistency checks of the GICC subtable of MADT */
>> -#define ACPI_MADT_GICC_LENGTH	\
>> -	(acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
>> +#define ACPI_MADT_GICC_MIN_LENGTH   ACPI_OFFSET(  \
>> +	struct acpi_madt_generic_interrupt, efficiency_class)
>>   
>>   #define BAD_MADT_GICC_ENTRY(entry, end)					\
>> -	(!(entry) || (entry)->header.length != ACPI_MADT_GICC_LENGTH ||	\
>> -	(unsigned long)(entry) + ACPI_MADT_GICC_LENGTH > (end))
>> +	(!(entry) || (entry)->header.length < ACPI_MADT_GICC_MIN_LENGTH || \
>> +	(unsigned long)(entry) + (entry)->header.length > (end))
>>   
>>   /* Basic configuration for ACPI */
>>   #ifdef	CONFIG_ACPI
>> -- 
>> 2.14.3
>>