On 8/31/20 8:40 AM, Christoph Hellwig wrote:

On Sun, Aug 30, 2020 at 11:04:21AM +0200, Cédric Le Goater wrote:

quoted

Hello,

On 7/8/20 5:24 PM, Christoph Hellwig wrote:

quoted

Use the DMA API bypass mechanism for direct window mappings.  This uses
common code and speed up the direct mapping case by avoiding indirect
calls just when not using dma ops at all.  It also fixes a problem where
the sync_* methods were using the bypass check for DMA allocations, but
those are part of the streaming ops.

Note that this patch loses the DMA_ATTR_WEAK_ORDERING override, which
has never been well defined, as is only used by a few drivers, which
IIRC never showed up in the typical Cell blade setups that are affected
by the ordering workaround.

Fixes: efd176a04bef ("powerpc/pseries/dma: Allow SWIOTLB")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/powerpc/Kconfig              |  1 +
 arch/powerpc/include/asm/device.h |  5 --
 arch/powerpc/kernel/dma-iommu.c   | 90 ++++---------------------------
 3 files changed, 10 insertions(+), 86 deletions(-)

I am seeing corruptions on a couple of POWER9 systems (boston) when
stressed with IO. stress-ng gives some results but I have first seen
it when compiling the kernel in a guest and this is still the best way
to raise the issue.

These systems have of a SAS Adaptec controller :

  0003:01:00.0 Serial Attached SCSI controller: Adaptec Series 8 12G SAS/PCIe 3 (rev 01)

When the failure occurs, the POWERPC EEH interrupt fires and dumps
lowlevel PHB4 registers among which :
					  
  [ 2179.251069490,3] PHB#0003[0:3]:           phbErrorStatus = 0000028000000000
  [ 2179.251117476,3] PHB#0003[0:3]:      phbFirstErrorStatus = 0000020000000000

The bits raised identify a PPC 'TCE' error, which means it is related
to DMAs. See below for more details.


Reverting this patch "fixes" the issue but it is probably else where,
in some other layers or in the aacraid driver. How should I proceed 
to get more information ?

The aacraid DMA masks look like a mess.  Can you try the hack
below and see it it helps?

No effect. The system crashes the same. But Alexey spotted some issue 
with swiotlb.

C.