Re: [PATCH] net/usb: rtl8150: allocate URB transfer_buffer and setup_packet separately

On 09.08.2013 21:50, Petko Manolov wrote:

On Thu, 8 Aug 2013, Jussi Kivilinna wrote:

quoted

On 08.08.2013 18:14, Petko Manolov wrote:

quoted

On Wed, 7 Aug 2013, Jussi Kivilinna wrote:

quoted

rtl8150 allocates URB transfer_buffer and setup_packet as part of same 
structure 'struct async_req'. This can cause same cacheline to be 
DMA-mapped twice with same URB. This can lead to memory corruption on 
some systems.

I can see performance impact due to the double mapping.  However, memory 
corruption seems a bit too much for sane cache and DMA controllers.  Out 
of interest - which is the architecture that will potentially corrupt the 
memory.

rtlwifi driver had similar structure to allocate both setup_packet and 
transfer_buffer in single go (overlapping dma-mapping cachelines) and 
this caused problems on ARM/sunxi. Problems means: memory corruptions at 
random locations, device freezes and lock-ups.

Broken controllers?..

At first I thought so too, but I discussed about this at linux-usb, and answer
was that driver which uses same (dma/-)cacheline for multiple buffers is buggy..
  http://marc.info/?l=linux-usb&m=137130407121137&w=2 (at end)
  http://marc.info/?l=linux-usb&m=137137080902265&w=2
  http://marc.info/?l=linux-usb&m=137242422120782&w=2

-Jussi