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.
