Re: PCI: disable I/O or mem before probing BAR size

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Mon, 4 May 2020 17:56:13 -0400 (EDT)
Mouse <mouse%Rodents-Montreal.ORG@localhost> wrote:

> >>> I found that Xen doesn't allow changing memory-mapped PCI BARs if
> >>> memory decode is enabled in the command register.  
> >> Is this permitted behaviour for a PCI device [...]?  
> > I think disabling access to whatever the BAR maps while fudging with
> > it is a pretty good idea on its own.  
> 
> On the one hand, yes, that's reasonable.
> 
> On the other, if anything else could possibly be poking at the device
> while you're probing its mapping register to see how big it is, you've
> got much worse problems already.

I was more thinking of other devices living wherever the BAR you're
messing with could end up, however short.

have fun
Michael