> How come that the functionality that is missing magically appears for some people?
Coincidence. Nobody on this bug report has reported that they've been able to run x86 binary X with a native compiled qemu but not with a cross compiled version of the same qemu sources. I think it is vastly more likely that the people who find that some of their code works are using differently compiled x86 binaries which happen not to use a glibc which provokes the 'invalid syscall' issue [ie fork() does not end up doing a clone syscall with whatever flags are causing us to return EINVAL].
> How come that the functionality that is missing magically appears for some people?
Coincidence. Nobody on this bug report has reported that they've been able to run x86 binary X with a native compiled qemu but not with a cross compiled version of the same qemu sources. I think it is vastly more likely that the people who find that some of their code works are using differently compiled x86 binaries which happen not to use a glibc which provokes the 'invalid syscall' issue [ie fork() does not end up doing a clone syscall with whatever flags are causing us to return EINVAL].