Re: kvm [2087]: load/store instruction decoding not implemented

["Richard W.M. Jones" <rjones@redhat.com>]

> On 24/02/15 14:36, Richard W.M. Jones wrote:
> > I can probably bisect this given time, but I'm going to try putting
> > some debug into the userspace process to find out which system call
> > fails first.

Perhaps not surprisingly, it's the init_module syscall which causes
the failure, ie. this line of code:

  https://github.com/libguestfs/supermin/blob/master/src/init.c#L436

I've no idea why that code would call copy_to_user.  It should be
copying the other way ...

It also fails on the first call to init_module, so the fact that it's
loading crc32-arm64.ko may just be a coincidence.

There are no other userspace processes running, but just to be sure
that it's not some other process in the guest, I also added a sleep
before the call to init_module, but same result as above.

I also looked at the implementation of init_module in glibc, but
AFAICT init_module is a straight syscall and glibc is not involved.

I also looked to see if I was calling init_module correctly on aarch64
(in case it has a different # of arguments of something) but it's
called in the same way in the libkmod code, so I think we're OK.

Next up, I will have a go at bisecting the guest kernel.

Rich.

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