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Re: [Qemu-ppc] [PATCH 11/25] spapr: describe the XIVE interrupt source f

From: Cédric Le Goater
Subject: Re: [Qemu-ppc] [PATCH 11/25] spapr: describe the XIVE interrupt source flags
Date: Sat, 2 Dec 2017 15:38:44 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

On 12/02/2017 03:24 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2017-11-28 at 17:40 +1100, David Gibson wrote:
>>> @@ -368,6 +368,10 @@ static void spapr_xive_realize(DeviceState *dev, Error 
>>> **errp)
>>>      /* Allocate the IVT (Interrupt Virtualization Table) */
>>>      xive->ivt = g_malloc0(xive->nr_irqs * sizeof(XiveIVE));
>>> +    /* All sources are emulated under the XIVE object and share the
>>> +     * same characteristic */
>>> +    xive->flags = XIVE_SRC_TRIGGER;
>> You never actually use this field.  And since it always has the same
>> value, is there a point to storing it?
> Some HW sources don't have it, so with pass-through maybe...

Hmm, yes. So, the current design for sPAPR handles all sources 
under the same XIVE object with a global memory region for all 
the ESBs. 

The first RFC had a mechanism to register source objects into 
the XIVE main one, allocating the IRQs per source and mapping 
the ESBs in the overall region. A bit like OPAL does. I then 
simplified for the sake of clarity and merged everything under 
the same XIVE object. 

Shall I reintroduce multiples sources support ? and provide a 
default one for IPIs and virtual devices of the machine. 




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