linux-kernel - Re: [PATCH 5/7] xen/events: drop xen_allocate_irqs

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Message-ID: <8ea75027-7e0f-4ea7-8bad-219d67ebae2f@epam.com>
Date:   Tue, 14 Nov 2023 18:29:35 +0000
From:   Oleksandr Tyshchenko <Oleksandr_Tyshchenko@...m.com>
To:     Juergen Gross <jgross@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Stefano Stabellini <sstabellini@...nel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH 5/7] xen/events: drop xen_allocate_irqs_dynamic()



On 14.11.23 10:35, Juergen Gross wrote:


Hello Juergen


> On 14.11.23 09:20, Oleksandr Tyshchenko wrote:
>>
>>
>> On 16.10.23 09:28, Juergen Gross wrote:
>>
>>
>> Hello Juergen
>>
>>> Instead of having a common function for allocating a single IRQ or a
>>> consecutive number of IRQs, split up the functionality into the callers
>>> of xen_allocate_irqs_dynamic().
>>>
>>> This allows to handle any allocation error in xen_irq_init() gracefully
>>> instead of panicing the system. Let xen_irq_init() return the irq_info
>>> pointer or NULL in case of an allocation error.
>>>
>>> Additionally set the IRQ into irq_info already at allocation time, as
>>> otherwise the IRQ would be '0' (which is a valid IRQ number) until
>>> being set.
>>>
>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>> ---
>>>    drivers/xen/events/events_base.c | 74 
>>> +++++++++++++++++++-------------
>>>    1 file changed, 44 insertions(+), 30 deletions(-)
>>>
>>
>> [snip]
>>
>>> @@ -1725,6 +1738,7 @@ void rebind_evtchn_irq(evtchn_port_t evtchn, 
>>> int irq)
>>>           so there should be a proper type */
>>>        BUG_ON(info->type == IRQT_UNBOUND);
>>> +    info->irq = irq;
>>
>>
>> I failed to understand why this is added here. Doesn't irq remain the
>> same, and info->irq remains valid? Could you please clarify.
> 
> The IRQ remains the same, but the event channel could change.
> 
> This setting of info->irq compensates for the related removal in
> xen_irq_info_common_setup().


Thanks for the clarification, you can add my

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>

> 
>>
>> Other changes lgtm.
> 
> 
> Juergen
>