linux-kernel - RE: [PATCH 2/3] iommu/vt-d: Replace spin_lock with mutex to protect domain ida

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Message-ID: <BN9PR11MB52768FF211A4E8D034380A7D8C852@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Thu, 24 Apr 2025 07:38:18 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, "Will
 Deacon" <will@...nel.org>, Robin Murphy <robin.murphy@....com>, "Jason
 Gunthorpe" <jgg@...pe.ca>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/3] iommu/vt-d: Replace spin_lock with mutex to protect
 domain ida

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Wednesday, April 23, 2025 11:10 AM
> 
> The domain ID allocator is currently protected by a spin_lock. However,
> ida_alloc_range can potentially block if it needs to allocate memory to
> grow its internal structures.
> 
> Replace the spin_lock with a mutex which allows sleep on block. Thus,
> the memory allocation flags can be updated from GFP_ATOMIC to
> GFP_KERNEL
> to allow blocking memory allocations if necessary.
> 
> Introduce a new mutex, did_lock, specifically for protecting the domain
> ida. The existing spinlock will remain for protecting other intel_iommu
> fields.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

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