Re: [PATCH 0/3] Limiting pci access requests

[Bjorn Helgaas <helgaas@kernel.org>]

Hi Keith,

On Mon, Aug 08, 2016 at 01:14:24PM -0600, Keith Busch wrote:
> We observe that error handling and device hot removal creates many
> unnecessary config and memory accesses to devices, some of which are not
> even present. While we expect command processing to proceed, we observe
> on various platforms that the unnecessary accesses create instability
> with hardware performing completion synthesis, and slows down handling
> of such error events as well as normal IO processing.

Is there some hot removal path that we've suddenly starting exercising
more than we used to?  Can you give us any details of that?  I'm
wondering if there are any more generic fixes we can make.  These
patches seem good, but a little piece-meal, so it feels like there
could be more places where we trip over similar issues.

> This patch series aims to reduce unnecessary accesses.
> 
> Keith Busch (3):
>   pcie: Don't search capabilities on removed devices
>   pci/msix: Skip disabling removed devices
>   pcie/aer: Cache capability position
> 
>  drivers/pci/msi.c             |  5 +++++
>  drivers/pci/pci.c             |  2 +-
>  drivers/pci/pcie/aer/aerdrv.c | 38 +++++++++++++++++---------------------
>  drivers/pci/pcie/aer/aerdrv.h |  1 +
>  4 files changed, 24 insertions(+), 22 deletions(-)
> 
> -- 
> 2.7.2
> 
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