Re: [Qemu-devel] [PATCH] apic: Make APIC ID limit error message clearer

[Wainer dos Santos Moschetta <wainersm@redhat.com>]

On 11/26/2018 08:56 PM, Eduardo Habkost wrote:
> Remove the "apic initialization failed" prefix (it conveys no
> useful information), replace "invalid" with "too large", and add
> an error hint with two possible solutions for the problem.
>
> Before:
>
>    $ qemu-system-x86_64 -machine q35 -smp 256
>    qemu-system-x86_64: apic initialization failed. APIC ID 255 is invalid
>
> After:
>
>    $ qemu-system-x86_64 -machine q35 -smp 256 -display none
>    qemu-system-x86_64: APIC ID 255 is too large

I would keep the problem "apic initialization failed" sentence. "APIC ID 
255 is too large" is just the cause.

>    Possible solutions:
>    * Lowering the number of VCPUs on the -smp option
>    * Using accel=kvm,kernel-irqchip=on or accel=kvm,kernel-irqchip=split
>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> I'm not sure this is the best way to provide usage hints to the
> user.  Any suggestions?

As a noob, I can testify that this kind of suggestion is very useful 
although there seems to not have many on QEMU. On the other hand, I 
understand it can make qemu verbose and so annoy people. Thus, maybe 
those suggestions could be enabled/disabled via options (e.g. -show-hints)?

- Wainer

> ---
>   hw/intc/apic.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/intc/apic.c b/hw/intc/apic.c
> index 97ffdd820f..f08006334d 100644
> --- a/hw/intc/apic.c
> +++ b/hw/intc/apic.c
> @@ -886,8 +886,11 @@ static void apic_realize(DeviceState *dev, Error **errp)
>       APICCommonState *s = APIC(dev);
>   
>       if (s->id >= MAX_APICS) {
> -        error_setg(errp, "%s initialization failed. APIC ID %d is invalid",
> -                   object_get_typename(OBJECT(dev)), s->id);
> +        error_setg(errp, "APIC ID %d is too large", s->id);
> +        error_append_hint(errp,
> +            "Possible solutions:\n"
> +            "* Lowering the number of VCPUs on the -smp option\n"
> +            "* Using accel=kvm,kernel-irqchip=on or accel=kvm,kernel-irqchip=split\n");
>           return;
>       }
>