hw.pci.realloc_bars

[John Baldwin]

On Thursday, October 26, 2017 02:20:23 PM Bob Bishop wrote:
> Hi,
> 
> hw.pci.realloc_bars controls a mechanism that repositions a PCI memory resource if it can’t be successfully allocated at the default place.
> 
> It’s disabled by default - anyone know why?
> 
> Seems to me that because it only comes into play in an error case it would be harmless to have it enabled by default. That would have avoided a recent case where installation on the HPE Gen 10 microserver is tricky because its VGA suffers from this problem.
> 
> Thoughts?

It is disabled by default because it is risky.  A correct implementation
would first pre-reserve as many firmware/BIOS-assigned ranges as possible
and only then fallback to allocating resources from scratch.  Right now
it tries to realloc as soon as it fails which is before we've reserved
firmware-assigned resources of other devices in the system.

-- 
John Baldwin