linux-kernel - RE: [PATCH 3/4] ntb_perf: pass correct struct device to dma_alloc

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Date:   Fri, 7 Feb 2020 08:40:34 +0000
From:   "Nath, Arindam" <Arindam.Nath@....com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        "Mehta, Sanju" <Sanju.Mehta@....com>
CC:     "linux-ntb@...glegroups.com" <linux-ntb@...glegroups.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/4] ntb_perf: pass correct struct device to
 dma_alloc_coherent

[AMD Official Use Only - Internal Distribution Only]

> -----Original Message-----
> From: Logan Gunthorpe <logang@...tatee.com>
> Sent: Thursday, February 6, 2020 00:14
> To: Nath, Arindam <Arindam.Nath@....com>; Jon Mason
> <jdmason@...zu.us>; Dave Jiang <dave.jiang@...el.com>; Allen Hubbe
> <allenbh@...il.com>; Mehta, Sanju <Sanju.Mehta@....com>
> Cc: linux-ntb@...glegroups.com; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 3/4] ntb_perf: pass correct struct device to
> dma_alloc_coherent
> 
> 
> 
> On 2020-02-05 10:16 a.m., Arindam Nath wrote:
> > From: Sanjay R Mehta <sanju.mehta@....com>
> >
> > Currently, ntb->dev is passed to dma_alloc_coherent
> > and dma_free_coherent calls. The returned dma_addr_t
> > is the CPU physical address. This works fine as long
> > as IOMMU is disabled. But when IOMMU is enabled, we
> > need to make sure that IOVA is returned for dma_addr_t.
> > So the correct way to achieve this is by changing the
> > first parameter of dma_alloc_coherent() as ntb->pdev->dev
> > instead.
> >
> > Fixes: 5648e56 ("NTB: ntb_perf: Add full multi-port NTB API support")
> > Signed-off-by: Sanjay R Mehta <sanju.mehta@....com>
> > Signed-off-by: Arindam Nath <arindam.nath@....com>
> 
> Ugh, this has been fixed repeatedly and independently by a number of
> people. I sent a fix[1] in more than a year ago and Sanjay repeated the
> effort a couple months ago[2].
> 
> I have the same feed back for you that I had for him: once we fix the
> bug we should also go in and remove the now unnecessary
> dma_coerce_mask_and_coherent() calls in the drivers at the same time
> seeing it no longer makes any sense. My patch did this already.

Thanks Logan. I will include your patches in my next version of the set,
and mention you in the "From" tag.

Arindam

> 
> Thanks,
> 
> Logan
> 
> [1]
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