On Thursday, 01.10.2015 at 15:15, Antti Kantee wrote: > On 01/10/15 14:51, Martin Lucina wrote: > >On Wednesday, 30.09.2015 at 21:00, Andrew Stuart wrote: > >>>>Any ideas? > >> > >>I’m out of my depth technically here but on Linux you can send console > >>output to both VGA and serial. I don’t know if that is practical or > >>relevant here. > >>https://www.kernel.org/doc/Documentation/serial-console.txt > > > >We definitely don't want to do that by default because a) It's slow b) The > >platform might have something else on COM1. > > Isn't your assumption that if there's no VGA, there can never be anything > else on COM1 except a 115200/8N1 serial console?
Correct. Except that Xen HVM provides a VGA even when you don't want to use it, and no one seems to do so in practice. I want to detect the Xen case and just do the right thing -- the internet is full enough as it is of people asking "How do I get serial console output on Xen HVM to work". > > >Anyway, I've figured out the obvious answer, which is to detect Xen (or in > >fact other hypervisors) using CPUID and prefer the serial console if on > >Xen. Just trying to get it into a committable state... > > Console config (port,params) is needed in any case, so why not start from > that, and then see how to make things as convenient as possible (but no more > convenient than that!). "first make it right, then make it $improved". Console config would require - a) defining the relevant parameter and its possible syntax b) parsing it, which is currently done at a higher layer up the stack, and we need to know which console to use much earlier, at which point we can't use even e.g. libc str* interfaces That is quite a bit more work and a more invasive change than the current approach. Also, I've not yet had a user ask for console configuration, so I'm not convinced it's needed.
