linux-kernel - Re: [PATCH v4] PCI: vmd: Make vmd_dev::cfg_lock a raw_spinlock

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Message-ID: <20250220145127.GC1777078@rocinante>
Date: Thu, 20 Feb 2025 23:51:27 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-pci@...r.kernel.org,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	Ryo Takakura <ryotkkr98@...il.com>, bhelgaas@...gle.com,
	jonathan.derrick@...ux.dev, lpieralisi@...nel.org,
	manivannan.sadhasivam@...aro.org, nirmal.patel@...ux.intel.com,
	robh@...nel.org, rostedt@...dmis.org, kbusch@...nel.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev
Subject: Re: [PATCH v4] PCI: vmd: Make vmd_dev::cfg_lock a raw_spinlock_t.

Hello,

> The access to the PCI config space via pci_ops::read and pci_ops::write
> is a low-level hardware access. The functions can be accessed with
> disabled interrupts even on PREEMPT_RT. The pci_lock has been made a
> raw_spinlock_t for this purpose. A spinlock_t becomes a sleeping lock on
> PREEMPT_RT can not be acquired with disabled interrupts.
> The vmd_dev::cfg_lock is accessed in the same context as the pci_lock.
> 
> Make vmd_dev::cfg_lock a raw_spinlock_t.

Applied to controller/vmd, thank you!

	Krzysztof