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

[David Gibson]

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.

> 
> 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.
> 
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature