linux-kernel - RE: [PATCH v2 1/2] iommu: Use mutex instead of spinlock for iommu_device

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Message-ID: <BN9PR11MB5276E9618612DCF4DAE0CAE68C7E2@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Mon, 29 Jan 2024 08:04:35 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Jason Gunthorpe <jgg@...pe.ca>, Joerg
 Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, Robin Murphy
	<robin.murphy@....com>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 1/2] iommu: Use mutex instead of spinlock for
 iommu_device_list

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Friday, January 26, 2024 6:54 PM
> 
> The iommu_device_lock spinlock was used to protect the iommu device
> list. However, there is no requirement to access the iommu device
> list in interrupt context. Therefore, a mutex is sufficient.

I don't think that interrupt is the reason for spinlock otherwise
spin_lock_irqsave() should be used instead.

> 
> This also prepares for the next change, which will iterate the iommu
> device list and call the probe callback within the locking area.
> 

Given the touched paths are all slow paths:

Reviewed-by: Kevin Tian <kevin.tian@...el.com>