Re: rump_server, "panic: uvm_km_alloc failed" on module load

[Christoph Badura <bad%bsd.de@localhost>]

On Thu, Jul 10, 2025 at 06:27:59PM +0200, Nemanja Simonovic wrote:
> I tried asking this on users list but got no reply.

I saw it but didn't have time to reply yet.

> When trying to load modules to rump_server I am getting kernel
> "panic: uvm_km_alloc failed". Both with -m parameter and with
> rump.modload.

That message comes from:
https://nxr.netbsd.org/xref/src/sys/rump/librump/rumpkern/vm.c#888

> I not sure if I am doing something wrong or hitting a bug?

We do have 3 ATF tests that deal with rump module loading:

src/tests/rump/modautoload/t_modautoload.c
src/tests/rump/rumpkern/t_modcmd.c
src/tests/rump/rumpkern/t_modlinkset.c

These tests pass OK:
https://releng.netbsd.org/b5reports/amd64/2025/2025.07.10.11.44.12/test.log

But the use neither -m nor rump.modload.  Could be the implementation for
-m or rump.modload has bitrotted.  I don't know.
Could be you are doing something wrong.

Have you tried debugging this with gdb?

Set a break point in rumpkern/vmc line 878, the call to rumpuser_anonmap(),
and step through that function and see where it fails.

--chris