linux-kernel - Re: [PATCH 5/8] kmsan: convert kmsan_handle

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Message-ID: <CAG_fn=XWP-rpV-D2nV-a3wMbzqLn2T-43tyGnoS2AhVGU8oZMw@mail.gmail.com>
Date: Thu, 26 Jun 2025 19:43:06 +0200
From: Alexander Potapenko <glider@...gle.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>, Leon Romanovsky <leonro@...dia.com>, 
	Christoph Hellwig <hch@....de>, Jonathan Corbet <corbet@....net>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Robin Murphy <robin.murphy@....com>, 
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	Marco Elver <elver@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Jérôme Glisse <jglisse@...hat.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	iommu@...ts.linux.dev, virtualization@...ts.linux.dev, 
	kasan-dev@...glegroups.com, linux-trace-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH 5/8] kmsan: convert kmsan_handle_dma to use physical addresses

On Wed, Jun 25, 2025 at 3:19 PM Leon Romanovsky <leon@...nel.org> wrote:
>
> From: Leon Romanovsky <leonro@...dia.com>

Hi Leon,

>
> Convert the KMSAN DMA handling function from page-based to physical
> address-based interface.
>
> The refactoring renames kmsan_handle_dma() parameters from accepting
> (struct page *page, size_t offset, size_t size) to (phys_addr_t phys,
> size_t size).

Could you please elaborate a bit why this is needed? Are you fixing
some particular issue?

> A PFN_VALID check is added to prevent KMSAN operations
> on non-page memory, preventing from non struct page backed address,
>
> As part of this change, support for highmem addresses is implemented
> using kmap_local_page() to handle both lowmem and highmem regions
> properly. All callers throughout the codebase are updated to use the
> new phys_addr_t based interface.

KMSAN only works on 64-bit systems, do we actually have highmem on any of these?