Re: [Xen-devel] [PATCH] xen/hvc-console: Make it work with HVM guests.

[Ian Campbell <ian.campbell@citrix.com>]

On Fri, 2013-10-25 at 15:38 -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Oct 24, 2013 at 05:43:54PM +0100, Ian Campbell wrote:
> > But stepping back how/why is this function called on x86 when not
> > running under Xen? Wouldn't the use have to be using console=hvc or
> > earlyprintk=xen or something -- which strikes me as user error... IOW
> > can we not just nuke the check
> 
> It shouldn't - ever. On x86 it is called from the early PV bootup code.
> 
> I occasionaly use it when developing/debugging and as such want it working
> in HVM even during early bootup.

Does earlyprintk=ttyS0,cough not Just Work for HVM guests? That would
avoid all of this stuff and assuming it works would be preferable IMHO.

Anyway, if not, then given that the xen_cpuid_base case is entirely x86
specific perhaps we can abstract this as something like:

	if (xen_arch_raw_console(str))
		return

	dom0_write_console(...)

Then ARM:
	#define xen_arch_raw_console 0
and x86
	static inline int xen_arch_raw_console(str)
	{
		if (xen_domain())
			return 0;

		/* Do the outb thing */
		return 1;
	}

This would also avoid the need for #ifdef x86 in the main function which
Julien pointed out.

Ian.