From: Mike Rapoport <rppt@kernel.org>
To: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net,
graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org,
rdunlap@infradead.org, tj@kernel.org, jasonmiu@google.com,
dmatlack@google.com, skhawaja@google.com
Subject: Re: [PATCH v6 09/10] liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE
Date: Mon, 20 Oct 2025 11:03:27 +0300 [thread overview]
Message-ID: <aPXszzdehAbkPOAh@kernel.org> (raw)
In-Reply-To: <20251018171756.1724191-10-pasha.tatashin@soleen.com>
On Sat, Oct 18, 2025 at 01:17:55PM -0400, Pasha Tatashin wrote:
> Metadata is preserved via 512-bytes, which requires using slabs. Slabs
KHO memory preservation metadata is preserved in 512 byte chunks which
requires their allocation from slab allocator.
> are not safe to be used with KHO because of kfence, and because partial
Please add more details why kfence is not safe here.
> slabs may lead leaks to the next kernel. Change the size to be
> PAGE_SIZE.
>
> While this change could potentially increase metadata overhead on
> systems with sparsely preserved memory, this is being mitigated by
> ongoing work to reduce sparseness during preservation via 1G guest
> pages. Furthermore, this change aligns with future work on a stateless
> KHO, which will also use page-sized bitmaps for its radix tree metadata.
With the stateless memory preservation there would be no problem with
kfence, right?
Maybe we should accelerate the stateless preservation work?
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2025-10-20 8:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-18 17:17 [PATCH v6 00/10] liveupdate: Rework KHO for in-kernel users & Fix memory corruption Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 01/10] kho: allow to drive kho from within kernel Pasha Tatashin
2025-10-20 7:43 ` Mike Rapoport
2025-10-21 16:08 ` Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 02/10] kho: make debugfs interface optional Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 03/10] kho: drop notifiers Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 04/10] kho: add interfaces to unpreserve folios and page ranes Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 05/10] kho: don't unpreserve memory during abort Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 06/10] liveupdate: kho: move to kernel/liveupdate Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 07/10] kho: move kho debugfs directory to liveupdate Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 08/10] liveupdate: kho: warn and fail on metadata or preserved memory in scratch area Pasha Tatashin
2025-10-20 7:56 ` Mike Rapoport
2025-10-20 21:56 ` Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 09/10] liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE Pasha Tatashin
2025-10-20 8:03 ` Mike Rapoport [this message]
2025-10-20 22:09 ` Pasha Tatashin
2025-10-18 17:17 ` [PATCH v6 10/10] liveupdate: kho: allocate metadata directly from the buddy allocator Pasha Tatashin
2025-10-20 8:05 ` Mike Rapoport
2025-10-20 22:17 ` Pasha Tatashin
2025-10-20 8:34 ` [PATCH v6 00/10] liveupdate: Rework KHO for in-kernel users & Fix memory corruption Mike Rapoport
2025-10-20 13:46 ` Pasha Tatashin
2025-10-20 13:47 ` Pasha Tatashin
2025-10-20 18:12 ` Mike Rapoport
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