linux-kernel - Re: [PATCH v1 13/13] kho: Introduce high-level memory allocation API

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Message-ID: <CA+CK2bB51Df-m3nTOQ8kRh+M7q_fdnpRR5xcRHSEgM3Q2C9LSQ@mail.gmail.com>
Date: Fri, 14 Nov 2025 11:40:11 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: akpm@...ux-foundation.org, bhe@...hat.com, jasonmiu@...gle.com, 
	arnd@...db.de, coxu@...hat.com, dave@...ilevsky.ca, ebiggers@...gle.com, 
	graf@...zon.com, kees@...nel.org, linux-kernel@...r.kernel.org, 
	kexec@...ts.infradead.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 13/13] kho: Introduce high-level memory allocation API

On Fri, Nov 14, 2025 at 11:16 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Fri, Nov 14, 2025 at 10:53:58AM -0500, Pasha Tatashin wrote:
> > Currently, clients of KHO must manually allocate memory (e.g., via
> > alloc_pages), calculate the page order, and explicitly call
> > kho_preserve_folio(). Similarly, cleanup requires separate calls to
> > unpreserve and free the memory.
> >
> > Introduce a high-level API to streamline this common pattern:
> >
> > - kho_alloc_preserve(size): Allocates physically contiguous, zeroed
> >   memory and immediately marks it for preservation.
> > - kho_free_unpreserve(ptr, size): Unpreserves and frees the memory
> >   in the current kernel.
> > - kho_free_restore(ptr, size): Restores the struct page state of
> >   preserved memory in the new kernel and immediately frees it to the
> >   page allocator.
>
> It would have been nice to have it before patch 3 (Preserve FDT folio only
> once during initialization) and use kho_alloc_preserve() for KHO's own FDT.

Sure, I will move it before 3.

>
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> > ---
> >  include/linux/kexec_handover.h     |  22 +++++--
> >  kernel/liveupdate/kexec_handover.c | 101 +++++++++++++++++++++++++++++
> >  2 files changed, 116 insertions(+), 7 deletions(-)
>
> --
> Sincerely yours,
> Mike.