Re: [PATCH 07/32] mm: Bring back vmalloc_exec

[Kent Overstreet <kent.overstreet@linux.dev>]

On Sun, May 21, 2023 at 02:33:34PM -0700, Eric Biggers wrote:
> FYI, I had a go with your test framework today, but I ran into too many problems
> to really bother with it.  In case you want to improve it, these are the
> problems I ran into (so far).  The command I was trying to run, after having run
> './root_image create' as root as the README says to do, was
> 'build-test-kernel run -I ~/src/ktest/tests/bcachefs/perf.ktest':

Thanks for giving it a shot...

> - Error due to ~/src/ktest/tests/bcachefs/bcachefs-tools not existing.  Worked
>   around by cloning the bcachefs-tools repo to this location.  (Note, it's not a
>   git submodule, so updating the git submodules didn't help.)

a require-git line was missing, fixed that...

> - Error due to "Root image not found".  Worked around by recursively chown'ing
>   /var/lib/ktest from root to my user.  (Note, the README says to run
>   'root_image create' as root, which results in root ownership.)

Not sure about this one - root ownership is supposed to be fine because
qemu opens the root image read only, we use qemu's block device
in-memory snapshot mode. Was it just not readable by your user?

> - Error due to "cannot set up guest memory 'pc.ram': Cannot allocate memory".
>   Worked around by editing tests/bcachefs/perf.ktest to change config-mem from
>   32G to 16G.  (I have 32G memory total on this computer.)
 
I think 32G is excessive for the tests that actually need to be in this
file, dropping that back to 16G.

> - Error due to "failed to open /dev/vfio/10: No such file or directory".
>   Enabling CONFIG_VFIO and CONFIG_VFIO_PCI in my host kernel didn't help.  It
>   seems the test is hardcoded to expect PCI passthrough to be set up with a
>   specific device.  I'd have expected it to just set up a standard virtual disk.

Some of the tests in that file do need a fast device, but the tests
we're interested in do not - I'll split that up.

I just pushed fixes for everything except the root_image issue if you
want to give it another go.

Cheers,
Kent