linux-kernel - RE: [PATCH v2 00/26] IB: Optimize DMA mapping

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Date:   Sat, 14 Jan 2017 02:05:14 +0000
From:   "Estrin, Alex" <alex.estrin@...el.com>
To:     Bart Van Assche <Bart.VanAssche@...disk.com>,
        "dledford@...hat.com" <dledford@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [PATCH v2 00/26] IB: Optimize DMA mapping



> -----Original Message-----
> From: Bart Van Assche [mailto:Bart.VanAssche@...disk.com]
> Sent: Friday, January 13, 2017 5:00 PM
> To: Estrin, Alex <alex.estrin@...el.com>; dledford@...hat.com
> Cc: linux-kernel@...r.kernel.org; linux-rdma@...r.kernel.org;
> gregkh@...uxfoundation.org
> Subject: Re: [PATCH v2 00/26] IB: Optimize DMA mapping
> 
> On Fri, 2017-01-13 at 21:08 +0000, Estrin, Alex wrote:
> > It didn't fix the failure... Apparently there is an issue with generic
> > mapping itself.
> 
> Hello Alex,
> 
> The generic mapping code in lib/dma-virt.c works fine with at least the rxe
> driver. Additionally, as far as I can see the mapping code in lib/dma-virt.c
> is identical to the mapping in drivers/infiniband/sw/rdmavt/dma.c. What is
> not clear to me however is how my patches can have caused the SDMA engine
> error messages? As far as I can see the code in
> drivers/infiniband/hw/hfi1/sdma.c uses PCI DMA mapping operations instead of
> the generic dma_virt_ops. Is that correct?

Hi Bart,
If you refer to code like this 
from sdma.c: 
/* dma map the coalesce buffer */
                addr = dma_map_single(&dd->pcidev->dev,
..... 
please see hfi1/verbs.c @ hfi1_register_ib_device()  

'dma_device' field is initialized here
->	ibdev->dma_device = &dd->pcidev->dev;
	followed by 
	ret = rvt_register_device(&dd->verbs_dev.rdi);
	->	set_dma_ops(rdi->ibdev.dma_device, &dma_virt_ops);
 
Thanks,
Alex.