Re: [Xen-devel] [PATCH 09/24] xen/arm: compile and run xenbus

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jul 26, 2012 at 04:33:51PM +0100, Stefano Stabellini wrote:
> bind_evtchn_to_irqhandler can legitimately return 0 (irq 0): it is not
> an error.
> 
> If Linux is running as an HVM domain and is running as Dom0, use
> xenstored_local_init to initialize the xenstore page and event channel.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  drivers/xen/xenbus/xenbus_comms.c |    2 +-
>  drivers/xen/xenbus/xenbus_probe.c |   27 +++++++++++++++++----------
>  drivers/xen/xenbus/xenbus_xs.c    |    1 +
>  3 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/xen/xenbus/xenbus_comms.c 
> b/drivers/xen/xenbus/xenbus_comms.c
> index 52fe7ad..c5aa55c 100644
> --- a/drivers/xen/xenbus/xenbus_comms.c
> +++ b/drivers/xen/xenbus/xenbus_comms.c
> @@ -224,7 +224,7 @@ int xb_init_comms(void)
>               int err;
>               err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
>                                               0, "xenbus", &xb_waitq);
> -             if (err <= 0) {
> +             if (err < 0) {
>                       printk(KERN_ERR "XENBUS request irq failed %i\n", err);
>                       return err;
>               }
> diff --git a/drivers/xen/xenbus/xenbus_probe.c 
> b/drivers/xen/xenbus/xenbus_probe.c
> index b793723..3ae47c2 100644
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -729,16 +729,23 @@ static int __init xenbus_init(void)
>       xenbus_ring_ops_init();
>  
>       if (xen_hvm_domain()) {
> -             uint64_t v = 0;
> -             err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
> -             if (err)
> -                     goto out_error;
> -             xen_store_evtchn = (int)v;
> -             err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> -             if (err)
> -                     goto out_error;
> -             xen_store_mfn = (unsigned long)v;
> -             xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, 
> PAGE_SIZE);
> +             if (xen_initial_domain()) {
> +                     err = xenstored_local_init();
> +                     xen_store_interface =
> +                             phys_to_virt(xen_store_mfn << PAGE_SHIFT);
> +             } else {
> +                     uint64_t v = 0;
> +                     err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
> +                     if (err)
> +                             goto out_error;
> +                     xen_store_evtchn = (int)v;
> +                     err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> +                     if (err)
> +                             goto out_error;
> +                     xen_store_mfn = (unsigned long)v;
> +                     xen_store_interface =
> +                             ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
> +             }

This, and along with the Hybrid PV dom0 (not yet posted, but it was doing
similar manipulation here) is getting more and more like a rat-mess.


Any chance we can just abstract the three different XenStore access
ways and just have something like this:

        enum {
                USE_UNKNOWN
                USE_HVM,
                USE_PV,
                USE_LOCAL
                USE_ALREADY_INIT
        };
        int usage = USE_UNKNOWN;
        if (xen_pv_domain())
                usage = USE_PV;
        if (xen_hvm_domain())
                usage = USE_HVM;
        if (xen_initial_domain())
                usage = USE_LOCAL;

        if (xen_start_info->store_evtchn)
                usage = USE_ALREADY_INIT;
        
        .. other overwrites..

        switch (usage) {
                .. blah blah.
        }


>               xen_store_evtchn = xen_start_info->store_evtchn;
>               xen_store_mfn = xen_start_info->store_mfn;
> diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
> index d1c217b..f7feb3d 100644
> --- a/drivers/xen/xenbus/xenbus_xs.c
> +++ b/drivers/xen/xenbus/xenbus_xs.c
> @@ -44,6 +44,7 @@
>  #include <linux/rwsem.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <asm/xen/hypervisor.h>
>  #include <xen/xenbus.h>
>  #include <xen/xen.h>
>  #include "xenbus_comms.h"
> -- 
> 1.7.2.5

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