linux-kernel - Re: [PATCH v2 2/2] ACPI: HMAT: Fix initiator registration for single-initiator systems

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Message-ID: <20221116235455.74nqyfdcqe72mhbi@box.shutemov.name>
Date:   Thu, 17 Nov 2022 02:54:55 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Vishal Verma <vishal.l.verma@...el.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org,
        Chris Piper <chris.d.piper@...el.com>, nvdimm@...ts.linux.dev,
        linux-acpi@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Liu Shixin <liushixin2@...wei.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ACPI: HMAT: Fix initiator registration for
 single-initiator systems

On Wed, Nov 16, 2022 at 04:37:37PM -0700, Vishal Verma wrote:
> In a system with a single initiator node, and one or more memory-only
> 'target' nodes, the memory-only node(s) would fail to register their
> initiator node correctly. i.e. in sysfs:
> 
>   # ls /sys/devices/system/node/node0/access0/targets/
>   node0
> 
> Where as the correct behavior should be:
> 
>   # ls /sys/devices/system/node/node0/access0/targets/
>   node0 node1
> 
> This happened because hmat_register_target_initiators() uses list_sort()
> to sort the initiator list, but the sort comparision function
> (initiator_cmp()) is overloaded to also set the node mask's bits.
> 
> In a system with a single initiator, the list is singular, and list_sort
> elides the comparision helper call. Thus the node mask never gets set,
> and the subsequent search for the best initiator comes up empty.
> 
> Add a new helper to consume the sorted initiator list, and generate the
> nodemask, decoupling it from the overloaded initiator_cmp() comparision
> callback. This prevents the singular list corner case naturally, and
> makes the code easier to follow as well.
> 
> Cc: <stable@...r.kernel.org>
> Cc: Rafael J. Wysocki <rafael@...nel.org>
> Cc: Liu Shixin <liushixin2@...wei.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reported-by: Chris Piper <chris.d.piper@...el.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov