Am Montag, den 10.09.2018, 15:30 +0200 schrieb Gerd Hoffmann: > On Mon, Sep 10, 2018 at 01:31:08PM +0200, Gert Wollny wrote: > > Am Montag, den 10.09.2018, 12:53 +0200 schrieb Gerd Hoffmann: > > > > > > By default qemu doesn't use memfd for backing storage, you have > > > to > > > explicitly configure qemu that way (see qemu commit log of the > > > test > > > branch): > > > > > > qemu-system-x86_64 -m 2G > > > -object memory-backend-memfd,id=ram,size=2G > > > -numa node,memdev=ram" > > > > Thanks, but that doesn't seem to help. > > Note the memory is specified twice, once with -m, once for the > memory-backend-memfd object. The two must match of course (or, to be > exact, the sum of all memory backends must match the total memory, > but unless you want create a virtual numa machine there is no reason > to have multiple memory-backends). Qemu actually complained when it was not the same.
> > > Are there any host kernel configuration parameters or features that > > I should set (apart from enabling udmabuf)? > > I'm not aware of any unusual parameters required. My config is based > on rhel-7, then stripped down with localmodconfig, then enabled the > bits I want in my test kernel. I use Gentoo and my kernel is rather stripped down ... > > Oh, wait, CONFIG_MEMFD_CREATE could be the one. I guess I should add > a Kconfig dependency. This was enabled, so not sure what else could be missing, I guess I'll have to add some logging to get an idea. Best, Gert
