Re: [Xen-devel] [PATCH 12/13] arm/xen: Get event-channel irq through HVM_PARAM when booting with ACPI

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 17 Nov 2015, shannon.zhao@xxxxxxxxxx wrote:
> From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> 
> When booting with ACPI, it could get the event-channel irq through
> HVM_PARAM_CALLBACK_IRQ.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> ---
>  arch/arm/xen/enlighten.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 1373d6d..b8e9db8 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -25,6 +25,7 @@
>  #include <linux/cpufreq.h>
>  #include <linux/cpu.h>
>  #include <linux/console.h>
> +#include <linux/acpi.h>
>  
>  #include <linux/mm.h>
>  
> @@ -190,10 +191,24 @@ static int __init xen_guest_init(void)
>       if (!xen_domain())
>               return 0;
>  
> -     xen_events_irq = irq_of_parse_and_map(xen_node, 0);
> -     if (!xen_events_irq) {
> -             pr_err("Xen event channel interrupt not found\n");
> -             return -ENODEV;
> +     if (!acpi_disabled) {
> +             struct xen_hvm_param a;
> +
> +             a.domid = DOMID_SELF;
> +             a.index = HVM_PARAM_CALLBACK_IRQ;
> +             if (HYPERVISOR_hvm_op(HVMOP_get_param, &a)) {

If HYPERVISOR_hvm_op returns an error (ret != 0), I wouldn't bother
checking for the returned value and simply return error.

On the other hand, if HYPERVISOR_hvm_op is successful (ret == 0), then
it might make sense to check for (a.value >> 56) == 3.


> +                     if ((a.value >> 56) != 3) {
> +                             pr_err("Can't get Xen event-channel irq\n");
> +                             return -ENODEV;
> +                     }
> +             }
> +             xen_events_irq = a.value & 0xff;
> +     } else {
> +             xen_events_irq = irq_of_parse_and_map(xen_node, 0);
> +             if (!xen_events_irq) {
> +                     pr_err("Xen event channel interrupt not found\n");
> +                     return -ENODEV;

Please make the error message common and move it out of the if/else.


> +             }
>       }
>  
>       shared_info_page = (struct shared_info *)get_zeroed_page(GFP_KERNEL);
> -- 
> 2.1.0
> 

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