Re: [Qemu-devel] [PATCH v2 4/8] spapr: Move interrupt allocator to xics

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 05/21/2014 06:34 PM, Alexander Graf wrote:
> 
> On 15.05.14 11:59, Alexey Kardashevskiy wrote:
>> The current allocator returns IRQ numbers from a pool and does not
>> support IRQs reuse in any form as it did not keep track of what it
>> previously returned, it only keeps the last returned IRQ. Some use
>> cases such as PCI hot(un)plug may require IRQ release and reallocation.
>>
>> This moves an allocator from SPAPR to XICS.
>>
>> This switches IRQ users to use new API.
>>
>> This uses LSI/MSI flags to know if interrupt is allocated.
>>
>> The interrupt release function will be posted as a separate patch.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>   hw/intc/xics.c         | 88
>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>   hw/ppc/spapr.c         | 67 --------------------------------------
>>   hw/ppc/spapr_events.c  |  2 +-
>>   hw/ppc/spapr_pci.c     |  6 ++--
>>   hw/ppc/spapr_vio.c     |  2 +-
>>   include/hw/ppc/spapr.h | 10 ------
>>   include/hw/ppc/xics.h  |  2 ++
>>   trace-events           |  4 +++
>>   8 files changed, 99 insertions(+), 82 deletions(-)
>>
>> diff --git a/hw/intc/xics.c b/hw/intc/xics.c
>> index 83a809e..fdcbb3a 100644
>> --- a/hw/intc/xics.c
>> +++ b/hw/intc/xics.c
>> @@ -689,6 +689,94 @@ void xics_set_irq_type(XICSState *icp, int irq, bool
>> lsi)
>>       ics_set_irq_type(ics, irq - ics->offset, lsi);
>>   }
>>   +#define ICS_IRQ_FREE(ics, srcno)   \
>> +    (!((ics)->irqs[(srcno)].flags & (XICS_FLAGS_IRQ_MASK)))
>> +
>> +static int ics_find_free_block(ICSState *ics, int num, int alignnum)
>> +{
>> +    int first, i;
>> +
>> +    for (first = 0; first < ics->nr_irqs; first += alignnum) {
>> +        if (num > (ics->nr_irqs - first)) {
>> +            return -1;
>> +        }
>> +        for (i = first; i < first + num; ++i) {
>> +            if (!ICS_IRQ_FREE(ics, i)) {
>> +                break;
>> +            }
>> +        }
>> +        if (i == (first + num)) {
>> +            return first;
>> +        }
>> +    }
>> +
>> +    return -1;
>> +}
>> +
>> +int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi)
>> +{
>> +    ICSState *ics = &icp->ics[src];
>> +    int irq;
>> +
>> +    if (irq_hint) {
>> +        assert(src == xics_find_source(icp, irq_hint));
> 
> Could this ever get triggered by a guest? Why don't we just fail as if the
> IRQ wasn't available?

The @irq_hist is only used when the user specified IRQ in the command line,
this is why it is assert. And the guest never gets to choose IRQ number, it
receives numbers either via device tree (and QEMU puts those numbers there,
not SLOF) or ibm,change-msi (QEMU returns numbers).



-- 
Alexey