linux-kernel - Re: [PATCH v1 08/16] kmsan: convert kmsan_handle

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Message-ID: <20250814124448.GE699432@nvidia.com>
Date: Thu, 14 Aug 2025 09:44:48 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Abdiel Janulgue <abdiel.janulgue@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>, Danilo Krummrich <dakr@...nel.org>,
	iommu@...ts.linux.dev, Jason Wang <jasowang@...hat.com>,
	Jens Axboe <axboe@...nel.dk>, Joerg Roedel <joro@...tes.org>,
	Jonathan Corbet <corbet@....net>, Juergen Gross <jgross@...e.com>,
	kasan-dev@...glegroups.com, Keith Busch <kbusch@...nel.org>,
	linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-nvme@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
	linux-trace-kernel@...r.kernel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Robin Murphy <robin.murphy@....com>, rust-for-linux@...r.kernel.org,
	Sagi Grimberg <sagi@...mberg.me>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	virtualization@...ts.linux.dev, Will Deacon <will@...nel.org>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v1 08/16] kmsan: convert kmsan_handle_dma to use physical
 addresses

On Thu, Aug 14, 2025 at 03:35:06PM +0300, Leon Romanovsky wrote:
> > Then check attrs here, not pfn_valid.
> 
> attrs are not available in kmsan_handle_dma(). I can add it if you prefer.

That makes more sense to the overall design. The comments I gave
before were driving at a promise to never try to touch a struct page
for ATTR_MMIO and think this should be comphrensive to never touching
a struct page even if pfnvalid.

> > > So let's keep this patch as is.
> > 
> > Still need to fix the remarks you clipped, do not check PageHighMem
> > just call kmap_local_pfn(). All thie PageHighMem stuff is new to this
> > patch and should not be here, it is the wrong way to use highmem.
> 
> Sure, thanks

I am wondering if there is some reason it was written like this in the
first place. Maybe we can't even do kmap here.. So perhaps if there is
not a strong reason to change it just continue to check pagehighmem
and fail.

if (!(attrs & ATTR_MMIO) && PageHighMem(phys_to_page(phys)))
   return;

Jason