linux-kernel - Re: DMA-API mapping errors in vmw

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Message-ID: <1395076090.2227.29.camel@dabdike.int.hansenpartnership.com>
Date:	Mon, 17 Mar 2014 10:08:10 -0700
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Josh Boyer <jwboyer@...oraproject.org>
Cc:	Arvind Kumar <arvindkumar@...are.com>,
	VMware PV-Drivers <pv-drivers@...are.com>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: DMA-API mapping errors in vmw_pvscsi

On Mon, 2014-03-17 at 12:52 -0400, Josh Boyer wrote:
> Hi All,
> 
> We've had a few reports[1][2] now on the vmw_pvscsi driver throwing
> DMA-API mapping errors when the DMA_API_DEBUG option is enabled.  I've
> included one from a recent 3.14-rc6 kernel below.  Looking at
> vmw_pvscsi.c, I can see pvscsi_map_buffers is missing the calls to
> pci_dma_mapping_error, which is what causes the warnings to be thrown.
> 
> However, I'm not familiar with this driver and I can't see what the
> proper error path should be in this case.  pvscsi_map_buffers is a
> void function and doesn't currently have the ability to return an
> error to the caller.  Even if it did, I'm not sure what the proper
> response to an error should be.  Thoughts?

It's missing checking in two places: from pci_map_single() and on
scsi_dma_map().  In the latter case, pvscsi_map_buffers needs to return
an error code and then pvscsi_queue_ring can return -1.

James


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