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From: Leon Romanovsky <leon@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
	jgg@ziepe.ca, zyjzyj2000@gmail.com,
	Daisuke Matsuda <dskmtsd@gmail.com>
Subject: Re: [PATCH for-next v3] RDMA/core: Avoid hmm_dma_map_alloc() for virtual DMA devices
Date: Mon, 26 May 2025 12:07:22 +0300	[thread overview]
Message-ID: <20250526090722.GY7435@unreal> (raw)
In-Reply-To: <aDQQyjJv9YKK_ZoV@infradead.org>

On Sun, May 25, 2025 at 11:57:14PM -0700, Christoph Hellwig wrote:
> On Sun, May 25, 2025 at 03:51:08AM -0400, Leon Romanovsky wrote:
> > 
> > On Sat, 24 May 2025 14:43:28 +0000, Daisuke Matsuda wrote:
> > > Drivers such as rxe, which use virtual DMA, must not call into the DMA
> > > mapping core since they lack physical DMA capabilities. Otherwise, a NULL
> > > pointer dereference is observed as shown below. This patch ensures the RDMA
> > > core handles virtual and physical DMA paths appropriately.
> > > 
> > > This fixes the following kernel oops:
> > > 
> > > [...]
> > 
> > Applied, thanks!
> 
> So while this version look correct, the idea of open coding the
> virtual device version of hmm_dma_map directly in the ODP code
> is a nasty leaky abstraction.  Please pull it into a proper ib_dma_*
> wrapper.

I did it on purpose as these ib_dma_* are used by all IB users (core, drivers
and ULPs) and at this point I don't want them to use any of that specific API.

Thanks 

  reply	other threads:[~2025-05-26  9:07 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-24 14:43 [PATCH for-next v3] RDMA/core: Avoid hmm_dma_map_alloc() for virtual DMA devices Daisuke Matsuda
2025-05-24 21:27 ` Greg Sword
2025-05-25  2:54   ` Daisuke Matsuda
2025-05-26 17:51     ` Greg Sword
2025-05-25  6:05   ` Leon Romanovsky
2025-05-26 17:52     ` Greg Sword
2025-05-27  6:35       ` Leon Romanovsky
2025-05-25  5:22 ` Zhu Yanjun
2025-05-25  6:03   ` Daisuke Matsuda
2025-05-25 14:17     ` Zhu Yanjun
2025-05-25  7:08 ` Leon Romanovsky
2025-05-25  9:34   ` Daisuke Matsuda
2025-05-25 10:24     ` Leon Romanovsky
2025-05-25  7:51 ` Leon Romanovsky
2025-05-26  6:57   ` Christoph Hellwig
2025-05-26  9:07     ` Leon Romanovsky [this message]
2025-05-26 19:57     ` Jason Gunthorpe

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