Re: [PATCH v2] s390x: adapter routes error handling

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 17.01.20 12:33, Cornelia Huck wrote:
> On Fri, 17 Jan 2020 12:22:45 +0100
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> 
>> On 17.01.20 12:11, Cornelia Huck wrote:
>>> If the kernel irqchip has been disabled, we don't want the
>>> {add,release}_adapter_routes routines to call any kvm_irqchip_*
>>> interfaces, as they may rely on an irqchip actually having been
>>> created. Just take a quick exit in that case instead.
>>>
>>> Also initialize routes->gsi[] with -1 in the virtio-ccw handling,
>>> to make sure we don't trip over other errors, either. (Nobody
>>> else uses the gsi array in that structure.)
>>>
>>> Fixes: d426d9fba8ea ("s390x/virtio-ccw: wire up irq routing and irqfds")
>>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>  
>>
>> I think it was actually quite good to see an error, because something went wrong
>> (kvmirqchip being off). Now the error (crash) was certainly a bad one.
>> What happens after this patch?
>> To me it _looks_ like every caller of set_guest_notifiers would get the ENOSYS
>> and bail out with an error so this should be ok, but it would be good
>> to add something to the patch description that says so.
>>
>> Something like "instead of crashing we now fail with an error message for vhost
>> and friends"
>> of course only if this is true.
> 
> It should work in the same way as it does for tcg right now (we return
> -ENOSYS in the non-kvm flic as well). If you're not using irqfd,
> everything will work just fine.
> 
> What about the following:
> 
> "If you are trying to use irqfd without a kernel irqchip, we will fail
> with an error."
> 

With that
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>