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SubjectRe: [PATCH 1/2] hvc_xen: support PV on HVM consoles
On Fri, 27 Jan 2012, Konrad Rzeszutek Wilk wrote:
> On Thu, Jan 26, 2012 at 12:43:26PM +0000, Stefano Stabellini wrote:
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > ---
> > drivers/tty/hvc/hvc_xen.c | 86 +++++++++++++++++++++++++++++-------
> > include/xen/interface/hvm/params.h | 6 ++-
> > 2 files changed, 75 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> > index 52fdf60..dd6641f 100644
> > --- a/drivers/tty/hvc/hvc_xen.c
> > +++ b/drivers/tty/hvc/hvc_xen.c
> > @@ -24,9 +24,12 @@
> > #include <linux/init.h>
> > #include <linux/types.h>
> >
> > +#include <asm/io.h>
> > #include <asm/xen/hypervisor.h>
> >
> > #include <xen/xen.h>
> > +#include <xen/interface/xen.h>
> > +#include <xen/hvm.h>
> > #include <xen/page.h>
> > #include <xen/events.h>
> > #include <xen/interface/io/console.h>
> > @@ -42,9 +45,13 @@ static int xencons_irq;
> > /* ------------------------------------------------------------------ */
> >
> > static unsigned long console_pfn = ~0ul;
> > +static unsigned int console_evtchn = ~0ul;
> > +static struct xencons_interface *xencons_if = NULL;
> >
> > static inline struct xencons_interface *xencons_interface(void)
> > {
> > + if (xencons_if != NULL)
> > + return xencons_if;
> > if (console_pfn == ~0ul)
> > return mfn_to_virt(xen_start_info->console.domU.mfn);
> > else
> > @@ -54,7 +61,10 @@ static inline struct xencons_interface *xencons_interface(void)
> > static inline void notify_daemon(void)
> > {
> > /* Use evtchn: this is called early, before irq is set up. */
> > - notify_remote_via_evtchn(xen_start_info->console.domU.evtchn);
> > + if (console_evtchn == ~0ul)
> > + notify_remote_via_evtchn(xen_start_info->console.domU.evtchn);
> > + else
> > + notify_remote_via_evtchn(console_evtchn);
> > }
> >
> > static int __write_console(const char *data, int len)
> > @@ -157,28 +167,65 @@ static struct hv_ops dom0_hvc_ops = {
> > .notifier_hangup = notifier_hangup_irq,
> > };
> >
> > +static int xen_hvm_console_init(void)
> > +{
> > + int r;
> > + uint64_t v = 0;
> > + unsigned long mfn;
> > +
> > + if (!xen_hvm_domain())
> > + return -ENODEV;
> > +
> > + if (xencons_if != NULL)
> > + return -EBUSY;
> > +
> > + r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
> > + if (r < 0)
> > + return -ENODEV;
> > + console_evtchn = v;
> > + hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
> > + if (r < 0)
> > + return -ENODEV;
>
> If we fail here, the console_evtchn is still going to be set
> meaning that "notify_daemon" will use the event channel. Thought
> I can't think of the notify daemon being called after the init had
> failed so this might not be an issue.
>
> > + mfn = v;
> > + xencons_if = ioremap(mfn << PAGE_SHIFT, PAGE_SIZE);
> > + if (xencons_if == NULL)
> > + return -ENODEV;
>
> Ditto. If we fail, we have the 'console_evtchn' set to something
> else than ~0UL.

Like you wrote, I think it doesn't matter.



> > + return 0;
> > +}
> > +
> > static int __init xen_hvc_init(void)
> > {
> > struct hvc_struct *hp;
> > struct hv_ops *ops;
> > + int r;
> >
> > - if (!xen_pv_domain())
> > + if (!xen_domain())
> > + return -ENODEV;
> > +
> > + if (xen_pv_domain() && !xen_initial_domain() &&
> > + !xen_start_info->console.domU.evtchn)
>
> Ewww.. What about just leaving the check:
> > return -ENODEV;
> >
> > if (xen_initial_domain()) {
> > ops = &dom0_hvc_ops;
> > xencons_irq = bind_virq_to_irq(VIRQ_CONSOLE, 0);
> > } else {
> > - if (!xen_start_info->console.domU.evtchn)
> > - return -ENODEV;
>
> this one as 'if (xen_pv_domain()) && !xen-..)
>
> That might make the code nicer to read?

Yes, good idea.


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