linux-kernel - Re: [PATCH v8 14/18] mm: memfd

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Message-ID: <2vxzecnshvat.fsf@kernel.org>
Date: Wed, 14 Jan 2026 19:02:34 +0000
From: Pratyush Yadav <pratyush@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>,  pratyush@...nel.org,
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Subject: Re: [PATCH v8 14/18] mm: memfd_luo: allow preserving memfd

On Wed, Jan 07 2026, Jason Gunthorpe wrote:

> On Tue, Nov 25, 2025 at 11:58:44AM -0500, Pasha Tatashin wrote:
>> From: Pratyush Yadav <ptyadav@...zon.de>
>> 
>> The ability to preserve a memfd allows userspace to use KHO and LUO to
>> transfer its memory contents to the next kernel. This is useful in many
>> ways. For one, it can be used with IOMMUFD as the backing store for
>> IOMMU page tables. Preserving IOMMUFD is essential for performing a
>> hypervisor live update with passthrough devices. memfd support provides
>> the first building block for making that possible.
>
> I would lead with the use of memfd to back the guest memory pages for
> use with KVM :)

I would assume using 1G-page-backed memfd is the more common use case,
and this patch doesn't come with 1G page support.

Anyway, the patch is now already applied so we can't go back and fix
the commit message...

-- 
Regards,
Pratyush Yadav