Re: PPC host with a PCI root-complex

[linas@austin.ibm.com (Linas Vepstas)]

On Thu, May 18, 2006 at 02:56:31PM -0700, Srinivas Murthy wrote:
> Hi,
> 
> We have a ppc host with a PCI root-complex across which there are multiple
> PCI end points.
> 
> An application running on the ppc host reading one of the device memory
> regions (not DMA access but direct CPU read) causes a parity error on the
> PCI interface controller.
> 
> We think that the error should be propagated up as a machine-check which is
> considered a non-recoverable system-wide error. However with multiple PCI
> devices present we think that this is too generic and could be reduced to be
> a critical-error which could be recovered from.

The "PCI Error Recovery" API was created to deal with this kind of a
situation. See Documentation/pci-error-recovery.txt

In breif: if something like a PCI parity error is detected by the
hardware, then some arch-specific code runs; for example,
 arch/powerpc/platforms/pseries/eeh.c.

This code notifies the PCI device driver (via generic callbacks in
include/linux/pci.h) about the error. The device driver may ask the
arch to have the pci device/bus/link/etc/ get reset, or not.  If/when
the PCI bus/link is back to normal, the PCI device driver is notified
via callback, and resumes normal operation.

If you have questions/suggestions, let me know, I've been maintaining 
this code, and am interested in seeing how well it can be adapted
to a broader range of hardware.

--linas