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Date: Mon, 24 Nov 2025 17:16:23 +0000
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Subject: Re: [PATCH] iommu: Remove redundant null check in
 iommu_iotlb_gather_queued
To: Will Deacon <will@kernel.org>, Aashish Sharma <aashish@aashishsharma.net>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>,
 Dmytro Maluka <dmaluka@google.com>, Joerg Roedel <joro@8bytes.org>,
 iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
 Aashish Sharma <shraash@google.com>
References: <20251111051952.1985154-1-aashish@aashishsharma.net>
 <aSSP7sG0OMFGElS9@willie-the-truck>
From: Robin Murphy <robin.murphy@arm.com>
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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.