linux-kernel - Re: [PATCH] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping

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Message-ID: <ZCGJn3QWhQl4F1dI@nvidia.com>
Date:   Mon, 27 Mar 2023 09:18:39 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     iommu@...ts.linux.dev, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Remove unnecessary locking in
 intel_irq_remapping_alloc()

On Tue, Mar 14, 2023 at 01:18:36PM +0800, Lu Baolu wrote:
> The global rwsem dmar_global_lock was introduced by commit 3a5670e8ac932
> ("iommu/vt-d: Introduce a rwsem to protect global data structures"). It
> is used to protect DMAR related global data from DMAR hotplug operations.
> 
> Using dmar_global_lock in intel_irq_remapping_alloc() is unnecessary as
> the DMAR global data structures are not touched there. Remove it to avoid
> below lockdep warning.

Tested-by: Jason Gunthorpe <jgg@...dia.com>

Solves my splat too

Let's send this to -rc please

Jason