From: Mika Westerberg
> Sent: 13 November 2017 10:22
> To: David Miller
> Cc: michael.ja...@intel.com; yehezkel.ber...@intel.com; netdev@vger.kernel.org
> Subject: Re: [PATCH net-next] net: thunderbolt: Clear finished Tx frame bus
> address in
> tbnet_tx_callback()
>
> On Sat, Nov 11, 2017 at 07:21:24PM +0900, David Miller wrote:
> > From: Mika Westerberg <mika.westerb...@linux.intel.com>
> > Date: Thu, 9 Nov 2017 13:46:28 +0300
> >
> > > When Thunderbolt network interface is disabled or when the cable is
> > > unplugged the driver releases all allocated buffers by calling
> > > tbnet_free_buffers() for each ring. This function then calls
> > > dma_unmap_page() for each buffer it finds where bus address is non-zero.
> > > Now, we only clear this bus address when the Tx buffer is sent to the
> > > hardware so it is possible that the function finds an entry that has
> > > already been unmapped.
> > >
> > > Enabling DMA-API debugging catches this as well:
> > >
> > > thunderbolt 0000:06:00.0: DMA-API: device driver tries to free DMA
> > > memory it has not allocated [device address=0x0000000068321000]
> > > [size=4096 bytes]
> > >
> > > Fix this by clearing the bus address of a Tx frame right after we have
> > > unmapped the buffer.
> > >
> > > Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
> >
> > Applied, but assuming zero is a non-valid DMA address is never a good
> > idea. That's why we have the DMA error code signaling abstracted.
>
> There does not seem to be a way to mark DMA address invalid in a driver
> so we probably need to add a flag to struct tbnet_frame instead.
Can you use the length?
David
