Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512

From: "Christoph Lameter (Ampere)" <cl@linux.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	 Mark Rutland <mark.rutland@arm.com>,
	 "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	 "Rafael J. Wysocki" <rafael@kernel.org>,
	Viresh Kumar <vireshk@kernel.org>,  Will Deacon <will@kernel.org>,
	Jonathan.Cameron@huawei.com,  Matteo.Carlini@arm.com,
	Valentin.Schneider@arm.com,  akpm@linux-foundation.org,
	anshuman.khandual@arm.com,  Eric Mackay <eric.mackay@oracle.com>,
	dave.kleikamp@oracle.com,  linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,  linux-mm@kvack.org,
	linux@armlinux.org.uk, robin.murphy@arm.com,
	 vanshikonda@os.amperecomputing.com, yang@os.amperecomputing.com,
	 Nishanth Menon <nm@ti.com>, Stephen Boyd <sboyd@kernel.org>
Subject: Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
Date: Fri, 8 Mar 2024 09:08:59 -0800 (PST)	[thread overview]
Message-ID: <e3952dc0-ec28-e7c7-e858-c47f146c93de@linux.com> (raw)
In-Reply-To: <f160a532-1d31-41a7-b8ae-de8575c395e9@samsung.com>

On Fri, 8 Mar 2024, Marek Szyprowski wrote:

>>>
>>> It looks that cpufreq-dt and/or opp drivers needs some adjustments
>>> related with this change.
>> That's strange. Is this with defconfig? I wonder whether NR_CPUS being
>> larger caused the issue with this specific code. Otherwise
>> CPUMASK_OFFSTACK may not work that well on arm64.

cpumask handling must use the accessor functions provided in 
include/linux/cpumask.h for declaring and accessing cpumasks. It is likely 
related to the driver opencoding one of the accessors.

I.e. you must use alloc_cpumask_var() and not allocate yourself on the 
stack.