On Tue, Aug 13, 2013 at 09:31:44PM +0100, Ian Campbell wrote:
> On Fri, 2013-08-09 at 10:55 -0400, Konrad Rzeszutek Wilk wrote:
> > The xen_raw_printk works great for debugging purposes and for
> > it print anything the Xen hypervisor has to be built with 'debug=y'.
> >
> > As such there is no difference between a PV or an PVHVM guest
> > using the hypercall, so lets use it.
> >
> > Lastly if the hyper-page is not setup yet (for example during
> > early HVM boot), then use the 0xe9 port if it has detected
> > that it is running under an Xen hypervisor.
>
> Does this really do what you say?
>
> I think xen_pv_domain returns false for a PVHVM guest, meaning that we
> only use the hypercall for proper PV guests and for PVHVM we use port
> 0xe9 until the hypercall page is setup at which point we silently
> discard any attempt to print via this mechanism.
>
'via this mechanism' refers to 0xe9 or dom0_write_console?
> or am I reading it wrong?
The code did have a bug as it would on HVM (after the hyper-page
was setup) still use 0xe9 instead of the dom0_write_console.
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.
Thanks for pointing this out!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
