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

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Message-ID: <c29136e0-054f-449d-b9f6-8116e3eea0c6@suse.com>
Date:   Tue, 14 Nov 2023 09:35:46 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Oleksandr Tyshchenko <Oleksandr_Tyshchenko@...m.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 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().

> 
> Other changes lgtm.


Juergen


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