Re: [Qemu-devel] [PATCH 08/10] ppc/xive: Extend XiveTCTX with an router object pointer

[Cédric Le Goater]

On 17/07/2019 04:08, David Gibson wrote:
> On Mon, Jul 15, 2019 at 05:45:38PM +0200, Cédric Le Goater wrote:
>> On 12/07/2019 03:15, David Gibson wrote:
>>> On Wed, Jul 03, 2019 at 07:54:57AM +0200, Cédric Le Goater wrote:
>>>> On 03/07/2019 04:07, David Gibson wrote:
>>>>> On Sun, Jun 30, 2019 at 10:45:59PM +0200, Cédric Le Goater wrote:
>>>>>> This is to perform lookups in the NVT table when a vCPU is dispatched
>>>>>> and possibly resend interrupts.
>>>>>
>>>>> I'm slightly confused by this one.  Aren't there multiple router
>>>>> objects, each of which can deliver to any thread?  In which case what
>>>>> router object is associated with a specific TCTX?
>>>>
>>>> when a vCPU is dispatched on a HW thread, the hypervisor does a store 
>>>> on the CAM line to store the VP id. At that time, it checks the IPB in 
>>>> the associated NVT structure and notifies the thread if an interrupt is 
>>>> pending. 
>>>>
>>>> We need to do a NVT lookup, just like the presenter in HW, hence the 
>>>> router pointer. You should look at the following patch which clarifies 
>>>> the resend sequence.
>>>
>>> Hm, ok.
>>>
>>>>>> Future XIVE chip will use a different class for the model of the
>>>>>> interrupt controller. So use an 'Object *' instead of a 'XiveRouter *'.
>>>>>
>>>>> This seems odd to me, shouldn't it be an interface pointer or
>>>>> something in that case?
>>>>
>>>> I have duplicated most of the XIVE models for P10 because the internal 
>>>> structures have changed. I managed to keep the XiveSource and XiveTCTX 
>>>> but we now have a Xive10Router, this is the reason why.
>>>
>>> Right, but XiveRouter and Xive10Router must have something in common
>>> if they can both be used here.  Usually that's expressed as a shared
>>> QOM interface - in which case you can use a pointer to the interface,
>>> rathe than using Object * which kind of implies *anything* can go
>>> here.
>>
>> Yeah. I also think it would be better to have a common base object but
>> the class don't have much in common. Here is what I have for now :
> 
> Uh.. QOM interfaces don't require there to be a common base object,
> only common methods.

It's not a QOM interface today because it already uses an interface. 

>>
>> P9:
>>
>> typedef struct XiveRouterClass {
>>     SysBusDeviceClass parent;
>>
>>     /* XIVE table accessors */
>>     int (*get_eas)(XiveRouter *xrtr, uint8_t eas_blk, uint32_t eas_idx,
>>                    XiveEAS *eas);
>>     int (*get_end)(XiveRouter *xrtr, uint8_t end_blk, uint32_t end_idx,
>>                    XiveEND *end);
>>     int (*write_end)(XiveRouter *xrtr, uint8_t end_blk, uint32_t end_idx,
>>                      XiveEND *end, uint8_t word_number);
>>     int (*get_nvt)(XiveRouter *xrtr, uint8_t nvt_blk, uint32_t nvt_idx,
>>                    XiveNVT *nvt);
>>     int (*write_nvt)(XiveRouter *xrtr, uint8_t nvt_blk, uint32_t nvt_idx,
>>                      XiveNVT *nvt, uint8_t word_number);
>>     XiveTCTX *(*get_tctx)(XiveRouter *xrtr, CPUState *cs);
>>     uint8_t (*get_block_id)(XiveRouter *xrtr);
>> } XiveRouterClass;
>>
>> and P10:
>>
>> typedef struct Xive10RouterClass {
>>     SysBusDeviceClass parent;
>>
>>     /* XIVE table accessors */
>>     int (*get_eas)(Xive10Router *xrtr, uint8_t eas_blk, uint32_t eas_idx,
>>                    Xive10EAS *eas);
>>     int (*get_end)(Xive10Router *xrtr, uint8_t end_blk, uint32_t end_idx,
>>                    Xive10END *end);
>>     int (*write_end)(Xive10Router *xrtr, uint8_t end_blk, uint32_t end_idx,
>>                      Xive10END *end, uint8_t word_number);
>>     int (*get_nvp)(Xive10Router *xrtr, uint8_t nvt_blk, uint32_t nvt_idx,
>>                    Xive10NVP *nvt);
>>     int (*write_nvp)(Xive10Router *xrtr, uint8_t nvt_blk, uint32_t nvt_idx,
>>                      Xive10NVP *nvt, uint8_t word_number);
>>     XiveTCTX *(*get_tctx)(Xive10Router *xrtr, CPUState *cs);
>>     uint8_t (*get_block_id)(XiveRouter *xrtr);
>>     uint32_t (*get_config)(Xive10Router *xrtr);
>> } Xive10RouterClass;
>>
>> Only get_tctx() is common. 
>>
>> The XIVE structures (END, NV*) used by the routing algo have changed a lot.
>> Even the presenter has changed, because all the CAM lines have a slightly 
>> different format.   
>>
>> C.
>>
>>
>