bhyve: Replace many fprintf(stderr, ...) calls with EPRINTLN

[jhb]

Summary

EPRINTLN handles newlines appropriately when stdout/stderr have been
reused as the backend for a serial port.

For bhyverun.c itself, the rule this attempts to follow is to use
regular fprintf/perror/warn/err prior to init_pci() (which is when
serial ports are configured) and to switch to EPRINTLN afterwards.

[markj]

Do you plan to convert uses of warn() as well?

[jhb]

In D42182#962551, @markj wrote:

Do you plan to convert uses of warn() as well?

I didn't have it in my plan as that requires a bit more work. There are probably several perror calls that also still need fixing after this. I had noticed the rdmsr messages recently in a Linux guest and went for the low-hanging fruit (initially just in vmexit.c but then expanding to what my a grep of fprintf found). There might still be some fprintf calls in snapshot.c that this change doesn't address.

[corvink]

usr.sbin/bhyve/bhyverun.c

955–956

Is it ok to use EPRINTLN if the serial port initialization of init_pci failed?

[jhb]

usr.sbin/bhyve/bhyverun.c

955–956

Yes, it's always safe to use as it just checks raw_stdio to determine if it should output "\r\n" vs "\n".