From: Pratyush Yadav <pratyush@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, rppt@kernel.org, tj@kernel.org,
jasonmiu@google.com, dmatlack@google.com, skhawaja@google.com
Subject: Re: [PATCH v3 2/3] liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE
Date: Wed, 22 Oct 2025 12:25:08 +0200 [thread overview]
Message-ID: <mafs0qzuvfd2z.fsf@kernel.org> (raw)
In-Reply-To: <20251021000852.2924827-3-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Mon, 20 Oct 2025 20:08:51 -0400")
On Mon, Oct 20 2025, Pasha Tatashin wrote:
> KHO memory preservation metadata is preserved in 512 byte chunks which
> requires their allocation from slab allocator. Slabs are not safe to be
> used with KHO because of kfence, and because partial slabs may lead
> leaks to the next kernel. Change the size to be PAGE_SIZE.
>
> The kfence specifically may cause memory corruption, where it randomly
> provides slab objects that can be within the scratch area. The reason
> for that is that kfence allocates its objects prior to KHO scratch is
> marked as CMA region.
>
> 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.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
[...]
--
Regards,
Pratyush Yadav
next prev parent reply other threads:[~2025-10-22 10:25 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-21 0:08 [PATCH v3 0/3] KHO: kfence + KHO memory corruption fix Pasha Tatashin
2025-10-21 0:08 ` [PATCH v3 1/3] liveupdate: kho: warn and fail on metadata or preserved memory in scratch area Pasha Tatashin
2025-10-22 10:22 ` Pratyush Yadav
2025-10-27 22:29 ` David Matlack
2025-10-28 0:01 ` Pasha Tatashin
2025-10-29 16:09 ` Jason Gunthorpe
2025-10-29 8:48 ` Mike Rapoport
2025-10-29 22:22 ` Pasha Tatashin
2025-10-29 22:35 ` Andrew Morton
2025-10-21 0:08 ` [PATCH v3 2/3] liveupdate: kho: Increase metadata bitmap size to PAGE_SIZE Pasha Tatashin
2025-10-22 10:25 ` Pratyush Yadav [this message]
2025-10-27 22:44 ` David Matlack
2025-10-27 22:56 ` David Matlack
2025-10-27 23:01 ` David Matlack
2025-10-28 0:03 ` Pasha Tatashin
2025-10-21 0:08 ` [PATCH v3 3/3] liveupdate: kho: allocate metadata directly from the buddy allocator Pasha Tatashin
2025-10-27 23:04 ` David Matlack
2025-10-28 0:03 ` Pasha Tatashin
2025-10-21 6:00 ` [PATCH v3 0/3] KHO: kfence + KHO memory corruption fix Mike Rapoport
2025-10-21 16:04 ` Pasha Tatashin
2025-10-21 20:53 ` Andrew Morton
2025-10-22 0:15 ` Pasha Tatashin
2025-10-22 5:48 ` Mike Rapoport
2025-10-22 18:24 ` Andrew Morton
2025-10-23 2:45 ` Andrew Morton
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