linux-kernel - Re: [PATCH v2 1/2] ACPI/PPTT: Add support for ACPI 6.3 thread flag

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <11fb712f-b3c2-5491-89ee-ea7efb18ddd8@arm.com>
Date:   Tue, 18 Jun 2019 16:28:32 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     John Garry <john.garry@...wei.com>,
        Valentin Schneider <valentin.schneider@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, will.deacon@....com, rjw@...ysocki.net,
        sudeep.holla@....com, lenb@...nel.org
Subject: Re: [PATCH v2 1/2] ACPI/PPTT: Add support for ACPI 6.3 thread flag

Hi,

On 6/18/19 12:23 PM, John Garry wrote:
> On 18/06/2019 15:40, Valentin Schneider wrote:
>> On 18/06/2019 15:21, Jeremy Linton wrote:
>> [...]
>>>>> + * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be 
>>>>> found or
>>>>> + *       the table revision isn't new enough.
>>>>> + * Otherwise returns flag value
>>>>> + */
>>>>
>>>> Nit: strictly speaking we're not returning the flag value but its mask
>>>> applied to the flags field. I don't think anyone will care about 
>>>> getting
>>>> the actual flag value, but it should be made obvious in the doc:
>>>
>>> Or I clarify the code to actually do what the comments says. Maybe 
>>> that is what John G was also pointing out too?
>>>
> 
> No, I was just saying that the kernel topology can be broken without 
> this series.
> 
>>
>> Mmm I didn't find any reply from John regarding this in v1, but I 
>> wouldn't
>> mind either way, as long as the doc & code are aligned.
>>
> 
> BTW, to me, function acpi_pptt_cpu_is_thread() seems to try to do too 
> much, i.e. check if the PPTT is new enough to support the thread flag 
> and also check if it is set for a specific cpu. I'd consider separate 
> functions here.

? Your suggesting replacing the


if (table->revision >= rev)
	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);

check with

if (revision_check(table, rev))
	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);


and a function like

static int revision_check(acpixxxx *table, int rev)
{
	return (table->revision >= rev);
}

Although, frankly if one were to do this, it should probably be a macro 
with the table type, and used in the dozen or so other places I found 
doing similar checks (spcr, iort, etc).

Or something else?




> 
> thanks,
> John
> 
>> [...]
>>
>> .
>>
> 
>