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Date:   Tue, 27 Oct 2020 09:11:03 +0100
From:   "hch@lst.de" <hch@lst.de>
To:     Parav Pandit <parav@nvidia.com>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        syzbot <syzbot+34dc2fea3478e659af01@syzkaller.appspotmail.com>,
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        "hch@lst.de" <hch@lst.de>,
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Subject: Re: WARNING in dma_map_page_attrs
Message-ID: <20201027081103.GA22877@lst.de>
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On Mon, Oct 26, 2020 at 05:23:48AM +0000, Parav Pandit wrote:
> Hi Christoph,
> 
> > From: Jakub Kicinski <kuba@kernel.org>
> > Sent: Saturday, October 24, 2020 11:45 PM
> > 
> > CC: rdma, looks like rdma from the stack trace
> > 
> > On Fri, 23 Oct 2020 20:07:17 -0700 syzbot wrote:
> > > syzbot has found a reproducer for the following issue on:
> > >
> > > HEAD commit:    3cb12d27 Merge tag 'net-5.10-rc1' of git://git.kernel.org/..
> 
> In [1] you mentioned that dma_mask should not be set for dma_virt_ops.
> So patch [2] removed it.
>
> But check to validate the dma mask for all dma_ops was added in [3].
> 
> What is the right way? Did I misunderstood your comment about dma_mask in [1]?

No, I did not say we don't need the mask.  I said copying over the
various dma-related fields from the parent is bogus.

I think rxe (and ther other drivers/infiniband/sw drivers) need a simple
dma_coerce_mask_and_coherent and nothing else.