Re: [patch 17/17] x86/fpu: Move FPU initialization into arch_cpu_finalize_init()

From: Guenter Roeck <linux@roeck-us.net>
To: Nikolay Borisov <nik.borisov@suse.com>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Linus Torvalds <torvalds@linux-foundation.org>,
	"Ahmed S. Darwish" <darwi@linutronix.de>,
	Arnd Bergmann <arnd@arndb.de>,
	Russell King <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	loongarch@lists.linux.dev,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	linux-m68k@lists.linux-m68k.org,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	linux-mips@vger.kernel.org,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-sh@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
	sparclinux@vger.kernel.org, Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-um@lists.infradead.org,
	Richard Henderson <richard.henderson@linaro.org>,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Chris Zankel <chris@zankel.net>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	semenzato@google.com
Subject: Re: [patch 17/17] x86/fpu: Move FPU initialization into arch_cpu_finalize_init()
Date: Fri, 1 Sep 2023 11:21:21 -0700	[thread overview]
Message-ID: <11390a1e-932f-8979-1547-f4555920fb7a@roeck-us.net> (raw)
In-Reply-To: <20f025f9-35d9-1f35-f21e-38e1bb44b74c@suse.com>

On 9/1/23 11:00, Nikolay Borisov wrote:
> 
> 
> On 1.09.23 г. 20:30 ч., Guenter Roeck wrote:
>> Hi,
>>
>> On Wed, Jun 14, 2023 at 01:39:46AM +0200, Thomas Gleixner wrote:
>>> Initializing the FPU during the early boot process is a pointless
>>> exercise. Early boot is convoluted and fragile enough.
>>>
>>> Nothing requires that the FPU is set up early. It has to be initialized
>>> before fork_init() because the task_struct size depends on the FPU register
>>> buffer size.
>>>
>>> Move the initialization to arch_cpu_finalize_init() which is the perfect
>>> place to do so.
>>>
>>> No functional change.
>>>
>>> This allows to remove quite some of the custom early command line parsing,
>>> but that's subject to the next installment.
>>>
>>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>>
>> The backport of this patch into chromeos-5.10 and chromeos-5.15 via stable
>> relase merges is causing various Chromebooks (not all of them) to crash
>> early during boot. Subsequent fixes have not addressed the problem for us,
>> so we already reverted the patch from chromeos-5.15 and will revert it
>> from chromeos-5.10 as well.
>>
>> I don't know if this is a Chromebook specific problem, or if it affects
>> mainline, so this is just a heads-up in case others experience similar
>> problems.
> 
> 
> Looking at 5.15 the following prerequisites are likely missing:
> 
> af8060279968 ("mm: Move mm_cachep initialization to mm_init()")
> 5b93a83649c7 ("x86/mm: Initialize text poking earlier")
> 
> 
> Can you test with those patches backported to 5.15.y and see if it works?

Both patches are already in v5.10.y and 5.15.y, so unfortunately
that doesn't help.

Guenter