linux-kernel - Re: [PATCH for-next v3] RDMA/core: Avoid hmm_dma_map

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Message-ID: <20250527063532.GZ7435@unreal>
Date: Tue, 27 May 2025 09:35:32 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Greg Sword <gregsword0@...il.com>
Cc: Daisuke Matsuda <dskmtsd@...il.com>, linux-kernel@...r.kernel.org,
	linux-rdma@...r.kernel.org, jgg@...pe.ca, zyjzyj2000@...il.com,
	hch@...radead.org
Subject: Re: [PATCH for-next v3] RDMA/core: Avoid hmm_dma_map_alloc() for
 virtual DMA devices

On Tue, May 27, 2025 at 01:52:58AM +0800, Greg Sword wrote:
> On Sun, May 25, 2025 at 2:05 PM Leon Romanovsky <leon@...nel.org> wrote:
> >
> > On Sun, May 25, 2025 at 05:27:23AM +0800, Greg Sword wrote:
> > > On Sat, May 24, 2025 at 10:43 PM Daisuke Matsuda <dskmtsd@...il.com> 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.
> >
> > <...>
> >
> > > > +EXPORT_SYMBOL(ib_dma_virt_map_alloc);
> > > >  #endif /* CONFIG_INFINIBAND_VIRT_DMA */
> > > >
> > >
> > > Your ODP patches have caused significant issues, including system
> > > instability. The latest version of your patches has led to critical
> > > failures in our environment. Due to these ongoing problems, we have
> > > decided that our system will no longer incorporate your patches going
> > > forward.
> >
> > Please be civil and appreciate the work done by other people. Daisuke
> > invested a lot of effort to implement ODP which is very non-trivial part
> > of RDMA HW.
> >
> > If you can do it better, just do it, we will be happy to merge your
> > patches too.
> >
> > At the end, we are talking about -next branch, which has potential to be
> > unstable, so next time provide detailed bug report to support your claims.
> >
> > In addition, it was me who broke RXE.
> 
> Is it an Honor?

It is a fact.

> 
> >
> > Thanks