Re: [Xen-devel] [PATCH] xen/hvc: If we use xen_raw_printk let it also work on HVM guests.

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

On Tue, 2013-08-13 at 21:59 +0100, Ian Campbell wrote:

> > What it should be is:
> > > >  
> > > >  void xen_raw_console_write(const char *str)
> > > >  {
> > > > -	dom0_write_console(0, str, strlen(str));
> > > > +	if (!xen_domain())
> > > > +		return;
> > > > +
> > > > +	if (xen_pv_domain())
> >             xen_domain()
> > 
> > > > +		dom0_write_console(0, str, strlen(str));
> > > > +	else if (xen_hvm_domain() || xen_cpuid_base()) {
> >      
> > 	else if (xen_cpuid_base()) {
> > 
> > > > +		/* The hyperpage has not been setup yet. */
> > > > +		int i, len = strlen(str);
> > > > +		for (i = 0; i < len; i++)
> > > > +			 outb(str[i], 0xe9);
> > > > +	}
> > > >  }
> > 
> > And then that should adhere to what I wrote up.
> 
> I think it does too.

Except as Daniel notes in <520A7145.5010306@tycho.nsa.gov> for unrelated
reasons:

>         HVM guests can still use the PV output - they just need to use the console
>         write hypercall instead of the HVM I/O port. I would think that PVH guests
>         would default to using the hypercall as it is more efficient (it takes a
>         string rather than one character per write).
>         
>         Actually, checking... the console_io hypercall would need to be added to
>         the hvm_hypercall{32,64}_table for an HVM guest to be able to use it; they
>         currently must use the I/O port. I didn't check the PVH patches.

Or did you actually try this code and it worked?

Ian.