linux-kernel - Re: [RFC PATCH 10/36] ACPI / MPAM: Parse the MPAM table

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: <370d63d1-3ab9-4da5-bac1-29b4229df3bd@arm.com>
Date: Tue, 5 Aug 2025 18:08:10 +0100
From: James Morse <james.morse@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 Rob Herring <robh@...nel.org>, Ben Horgan <ben.horgan@....com>,
 Rohit Mathew <rohit.mathew@....com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Zeng Heng
 <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>,
 Carl Worth <carl@...amperecomputing.com>,
 shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>
Subject: Re: [RFC PATCH 10/36] ACPI / MPAM: Parse the MPAM table

Hi Jonathan,

On 28/07/2025 11:08, Jonathan Cameron wrote:
>>> +static struct acpi_table_header *get_table(void)
>>> +{
>>> +	struct acpi_table_header *table;
>>> +	acpi_status status;
>>> +
>>> +	if (acpi_disabled || !system_supports_mpam())
>>> +		return NULL;
>>> +
>>> +	status = acpi_get_table(ACPI_SIG_MPAM, 0, &table);
>>> +	if (ACPI_FAILURE(status))
>>> +		return NULL;
>>> +
>>> +	if (table->revision != 1)
> 
> Missing an acpi_put_table()

Oops,


> I'm messing around with ACQUIRE() that is queued in the CXL tree
> for the coming merge window and noticed this.
> https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/log/?h=for-6.17/cleanup-acquire

(not more C++!)


> Interestingly this is a new corner case where we want conditional locking
> style handling but with return_ptr() style handling. Maybe too much of a niche
> to bother with infrastructure.
> 
> Worth noting though that one layer up it is probably worth something like:
> 
> DEFINE_FREE(acpi_table_mpam, struct acpi_table_header *, if (_T) acpi_put_table(_T));
> 
> That enables nice clean code like:
> 
> 
> static int __init acpi_mpam_parse(void)
> {
> 	struct acpi_table_header *mpam = __free(acpi_table_mpam) = get_table();
> 
> 	if (!mpam)
> 		return 0;
> 
> 	return _parse_table;
> }

I've got bits of that from your PPTT suggestions. I ended up folding the get_table()
helper in here.

count_msc() gets the same treatment and the cleanup thing lets _count_msc() be folded into it.


Thanks,

James


> This series was big enough that I'm spinning a single 'suggested changes'
> patch on top of it that includes stuff like this.  Might take another day or so.
> 
> Jonathan