Re: [PATCH v7] Add udmabuf misc device
From: Gert Wollny
Date: Mon Sep 10 2018 - 13:40:21 EST
Using the kernel 4.19.0-rc2 it works now, so With the fix for not
calling fput when memfd == NULL the patch is
Reviewed-By: Gert Wollny <gert.wollny@xxxxxxxxxxxxx>
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,
> unless you want create a virtual numa machine there is no reason to
> multiple memory-backends).
> > 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
> rhel-7, then stripped down with localmodconfig, then enabled the bits
> want in my test kernel.
> Oh, wait, CONFIG_MEMFD_CREATE could be the one. I guess I should add
> Kconfig dependency. Even though udmabuf will build just fine without
> that (because memfd is basically shmem with some features on top) it
> doesn't buy you much if the memfd_create syscall is not available ...