linux-kernel - Re: [PATCH] drm/panthor: Support partial unmaps of huge pages

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Message-ID: <c4639586-1bf0-4571-9e45-707fe7e7ba58@arm.com>
Date: Wed, 22 Oct 2025 05:55:23 +0100
From: Akash Goel <akash.goel@....com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: Adrián Larumbe <adrian.larumbe@...labora.com>,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 Steven Price <steven.price@....com>, kernel@...labora.com,
 Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH] drm/panthor: Support partial unmaps of huge pages



On 10/21/25 17:09, Boris Brezillon wrote:
> On Tue, 21 Oct 2025 15:32:45 +0100
> Akash Goel <akash.goel@....com> wrote:
> 
>> On 10/19/25 04:19, Adrián Larumbe wrote:
>>> Commit 33729a5fc0ca ("iommu/io-pgtable-arm: Remove split on unmap
>>> behavior") did away with the treatment of partial unmaps of huge IOPTEs.
>>>    
>>
>> Sorry have a doubt.
>>
>> Corresponding to the commit 33729a5fc0ca, can we now remove the code to
>> pre-allocate L3 page table pages i.e. 'op_ctx->rsvd_page_tables.pages'
>> inside panthor_vm_prepare_unmap_op_ctx() ?.
> 
> Well, not if we want to support partial unmaps of huge pages at a non-2M
> boundary.

Thanks Boris for clarifying.

Sorry I didn't consider that in order to support partial unmaps of huge 
pages at a non-2M boundary, we still need to call panthor_vm_map_pages() 
so as to remap the difference between the start/end of huge page and the 
start/end of the actual unmap range.

Best Regards
Akash