linux-kernel - Re: [PATCH v2] efi/unaccepted: touch soft lockup during memory accept

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Message-ID: <ZiZ2yUI09QIrYr/4@chenyu5-mobl2>
Date: Mon, 22 Apr 2024 22:40:09 +0800
From: Chen Yu <yu.c.chen@...el.com>
To: <linux-efi@...r.kernel.org>, Ard Biesheuvel <ardb@...nel.org>
CC: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Vlastimil Babka
	<vbabka@...e.cz>, Nikolay Borisov <nik.borisov@...e.com>, Chao Gao
	<chao.gao@...el.com>, <linux-kernel@...r.kernel.org>, "Hossain, Md Iqbal"
	<md.iqbal.hossain@...el.com>
Subject: Re: [PATCH v2] efi/unaccepted: touch soft lockup during memory accept

On 2024-04-11 at 08:49:07 +0800, Chen Yu wrote:
> Commit 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused
> by parallel memory acceptance") has released the spinlock so
> other CPUs can do memory acceptance in parallel and not
> triggers softlockup on other CPUs.
> 
> However the softlock up was intermittent shown up if the memory
> of the TD guest is large, and the timeout of softlockup is set
> to 1 second.
> 
> The symptom is:
> When the local irq is enabled at the end of accept_memory(),
> the softlockup detects that the watchdog on single CPU has
> not been fed for a while. That is to say, even other CPUs
> will not be blocked by spinlock, the current CPU might be
> stunk with local irq disabled for a while, which hurts not
> only nmi watchdog but also softlockup.
> 
> Chao Gao pointed out that the memory accept could be time
> costly and there was similar report before. Thus to avoid
> any softlocup detection during this stage, give the
> softlockup a flag to skip the timeout check at the end of
> accept_memory(), by invoking touch_softlockup_watchdog().
> 
> Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> Reported-by: "Hossain, Md Iqbal" <md.iqbal.hossain@...el.com>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> v1 -> v2:
> 	 Refine the commit log and add fixes tag/reviewed-by tag from Kirill.

Gently pinging about this patch.

thanks,
Chenyu