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

From: Catalin Marinas <catalin.marinas@arm.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	"Christoph Lameter (Ampere)" <cl@linux.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: Mon, 11 Mar 2024 15:22:00 +0000	[thread overview]
Message-ID: <Ze8hmCbN7_GDRMVS@arm.com> (raw)
In-Reply-To: <8abb1a69-6cbd-4a36-ab1d-d269cdafa391@samsung.com>

On Mon, Mar 11, 2024 at 03:56:37PM +0100, Marek Szyprowski wrote:
> On 11.03.2024 13:12, Mark Rutland wrote:
> > On Fri, Mar 08, 2024 at 09:08:59AM -0800, Christoph Lameter (Ampere) wrote:
> >> 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 took a look at both the OPP code and the cpufreq-dt code and it looks like
> > those are doign the right thing w.r.t. cpumask manipulation (i.e. they only use
> > the cpumask accessors, and use the cpumask_var_*() functions to dynamically
> > allocate/free cpumasks). Maybe I've missed something, but superficially those
> > look right.
> >
> > Marek, can you try reverting this commit and trying defconfig + NR_CPUS=512?
> 
> Yes, with $subject reverted and CONFIG_NR_CPUS=512 everything works 
> fine, so it must be something else broken.

Thanks for confirming. Would you mind testing the problematic commit
with CONFIG_DEBUG_PER_CPU_MAPS enabled? If it doesn't show anything
obvious that can be fixed quickly, I'll revert the commit and queue it
again after -rc1 for 6.10 (I haven't sent 6.9 the pull request yet).

-- 
Catalin