linux-kernel - Re: [PATCH] iommu: Remove redundant null check in iommu_iotlb_gather

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Message-ID: <78b9feb4-f756-4d44-9472-95ffad58647a@arm.com>
Date: Mon, 24 Nov 2025 17:16:23 +0000
From: Robin Murphy <robin.murphy@....com>
To: Will Deacon <will@...nel.org>, Aashish Sharma <aashish@...hishsharma.net>
Cc: Vineeth Pillai <vineeth@...byteword.org>,
 Dmytro Maluka <dmaluka@...gle.com>, Joerg Roedel <joro@...tes.org>,
 iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Aashish Sharma <shraash@...gle.com>
Subject: Re: [PATCH] iommu: Remove redundant null check in
 iommu_iotlb_gather_queued

On 2025-11-24 5:03 pm, Will Deacon wrote:
> On Mon, Nov 10, 2025 at 09:19:52PM -0800, Aashish Sharma wrote:
>> The callers of 'iommu_iotlb_gather_queued' always have a non-null
>> 'gather', so we don't need to check for the same in the function.
> 
> That's not obviously true to me, how did you check it?
> 
> For example, msm_iommu_pagetable_unmap() appears to call into
> io_pgtable_ops::unmap_pages() with a NULL gather pointer.

Indeed I think the only redundant check is the one which seems to have 
snuck into __arm_lpae_unmap() not so long ago (which the other callers 
never had and still don't.)

Thanks,
Robin.