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From: Thomas Gleixner <tglx@linutronix.de>
To: Zijiang Huang <huangzjsmile@gmail.com>, lukas@wunner.de
Cc: bhelgaas@google.com, flyingpeng@tencent.com,
	huangzjsmile@gmail.com, kerayhuang@tencent.com,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH] PCI: Using lockless config space accessors based on
Date: Wed, 07 May 2025 16:00:06 +0200	[thread overview]
Message-ID: <877c2smsgp.ffs@tglx> (raw)
In-Reply-To: <20250507090407.2146324-1-kerayhuang@tencent.com>

On Wed, May 07 2025 at 17:04, Zijiang Huang wrote:
> I think it's safe to make this change for user-space accessors as well,
> since user-space only reads from proc files.

Again. See pci_cfg_access_lock()

>> Why is performance of the user space accessors important?
>> Perhaps because of vfio?
>
> During stability testing on large-scale machines (384+ CPUs), we always                                             > observed that heavy concurrent user-space access to PCI config space triggers 
> kernel softlockups.
>  
> Reproduction method: stress-ng --pci 384 

This is not really interesting as stress-ng is not a real world work
load.

What's the actual real world use case which uses those interfaces so
that the lock becomes an issue?

Thanks,

        tglx

  reply	other threads:[~2025-05-07 14:00 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-07  7:30 [PATCH] PCI: Using lockless config space accessors based on Kconfig option Zijiang Huang
2025-05-07  7:53 ` Lukas Wunner
2025-05-07  9:04   ` [PATCH] PCI: Using lockless config space accessors based on Zijiang Huang
2025-05-07 14:00     ` Thomas Gleixner [this message]
2025-05-07  9:11   ` [PATCH] PCI: Using lockless config space accessors based on Kconfig option Thomas Gleixner

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