Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

From: Benjamin Herrenschmidt
Date: Tue Jun 11 2019 - 03:03:05 EST

On Tue, 2019-06-11 at 08:08 +0200, Christoph Hellwig wrote:
> On Tue, Jun 11, 2019 at 03:56:33PM +1000, Benjamin Herrenschmidt
> wrote:
> > The reason I think it sort-of-mostly-worked is that to get more
> > than
> > 1GB of RAM, those machines use CONFIG_HIGHMEM. And *most* network
> > buffers aren't allocated in Highmem.... so you got lucky.
> >
> > That said, there is such as thing as no-copy send on network, so I
> > wouldn't be surprised if some things would still have failed, just
> > not
> > frequent enough for you to notice.
> Unless NETIF_F_HIGHDMA is set on a netdev, the core networkign code
> will bounce buffer highmem pages for the driver under all
> circumstances.

... which b43legacy doesn't set to the best of my knowledge ...

Which makes me wonder how come it didn't work even with your patches ?
AFAIK, we have less than 1GB of lowmem unless the config has been