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SubjectRe: [PATCH 1/2] hvc_xen: support PV on HVM consoles
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.

> +
> + 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?

> -
> ops = &domU_hvc_ops;
> - xencons_irq = bind_evtchn_to_irq(xen_start_info->console.domU.evtchn);
> + if (xen_pv_domain()) {
> + console_pfn = mfn_to_pfn(xen_start_info->console.domU.mfn);
> + console_evtchn = xen_start_info->console.domU.evtchn;
> + } else {
> + r = xen_hvm_console_init();
> + if (r < 0)
> + return r;
> + }
> + xencons_irq = bind_evtchn_to_irq(console_evtchn);
> + if (xencons_irq < 0)
> + xencons_irq = 0; /* NO_IRQ */
> + else
> + irq_set_noprobe(xencons_irq);
> }
> - if (xencons_irq < 0)
> - xencons_irq = 0; /* NO_IRQ */
> - else
> - irq_set_noprobe(xencons_irq);
>
> hp = hvc_alloc(HVC_COOKIE, xencons_irq, ops, 256);
> if (IS_ERR(hp))
> @@ -186,15 +233,13 @@ static int __init xen_hvc_init(void)
>
> hvc = hp;
>
> - console_pfn = mfn_to_pfn(xen_start_info->console.domU.mfn);
> -
> return 0;
> }
>
> void xen_console_resume(void)
> {
> if (xencons_irq)
> - rebind_evtchn_irq(xen_start_info->console.domU.evtchn, xencons_irq);
> + rebind_evtchn_irq(console_evtchn, xencons_irq);
> }
>
> static void __exit xen_hvc_fini(void)
> @@ -205,16 +250,22 @@ static void __exit xen_hvc_fini(void)
>
> static int xen_cons_init(void)
> {
> - struct hv_ops *ops;
> + const struct hv_ops *ops;
>
> - if (!xen_pv_domain())
> + if (!xen_domain())
> return 0;
>
> if (xen_initial_domain())
> ops = &dom0_hvc_ops;
> - else
> + else {
> ops = &domU_hvc_ops;
>
> + if (xen_pv_domain())
> + console_evtchn = xen_start_info->console.domU.evtchn;
> + else
> + xen_hvm_console_init();
> + }
> +
> hvc_instantiate(HVC_COOKIE, 0, ops);
> return 0;
> }
> @@ -230,6 +281,9 @@ static void xenboot_write_console(struct console *console, const char *string,
> unsigned int linelen, off = 0;
> const char *pos;
>
> + if (!xen_pv_domain())
> + return;
> +
> dom0_write_console(0, string, len);
>
> if (xen_initial_domain())
> diff --git a/include/xen/interface/hvm/params.h b/include/xen/interface/hvm/params.h
> index 1888d8c..1b4f923 100644
> --- a/include/xen/interface/hvm/params.h
> +++ b/include/xen/interface/hvm/params.h
> @@ -90,6 +90,10 @@
> /* Boolean: Enable aligning all periodic vpts to reduce interrupts */
> #define HVM_PARAM_VPT_ALIGN 16
>
> -#define HVM_NR_PARAMS 17
> +/* Console debug shared memory ring and event channel */
> +#define HVM_PARAM_CONSOLE_PFN 17
> +#define HVM_PARAM_CONSOLE_EVTCHN 18
> +
> +#define HVM_NR_PARAMS 19
>
> #endif /* __XEN_PUBLIC_HVM_PARAMS_H__ */
> --
> 1.7.2.5


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