[PATCH v2] spapr/xive: Use the xics flag to check for XIVE-only IRQ backends

[PATCH v2] spapr/xive: Use the xics flag to check for XIVE-only IRQ backends

[Cédric Le Goater]

The sPAPR machine has four different IRQ backends, each implementing
the XICS or XIVE interrupt mode or both in the case of the 'dual'
backend.

If a machine is started in P8 compat mode, QEMU should necessarily
support the XICS interrupt mode and in that case, the XIVE-only IRQ
backend is invalid. Currently, spapr_irq_check() tests the pointer
value to the IRQ backend to check for this condition, instead use the
'xics' flag. It's equivalent and it will ease the introduction of new
XIVE-only IRQ backends if needed.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 hw/ppc/spapr_irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
index 80cf1c3d6bb2..d036c8fef519 100644
--- a/hw/ppc/spapr_irq.c
+++ b/hw/ppc/spapr_irq.c
@@ -172,7 +172,7 @@ static int spapr_irq_check(SpaprMachineState *spapr, Error **errp)
          * To cover both and not confuse the OS, add an early failure in
          * QEMU.
          */
-        if (spapr->irq == &spapr_irq_xive) {
+        if (!spapr->irq->xics) {
             error_setg(errp, "XIVE-only machines require a POWER9 CPU");
             return -1;
         }
-- 
2.25.4

Re: [PATCH v2] spapr/xive: Use the xics flag to check for XIVE-only IRQ backends

[David Gibson]

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On Thu, Aug 20, 2020 at 04:01:06PM +0200, Cédric Le Goater wrote:
> The sPAPR machine has four different IRQ backends, each implementing
> the XICS or XIVE interrupt mode or both in the case of the 'dual'
> backend.
> 
> If a machine is started in P8 compat mode, QEMU should necessarily
> support the XICS interrupt mode and in that case, the XIVE-only IRQ
> backend is invalid. Currently, spapr_irq_check() tests the pointer
> value to the IRQ backend to check for this condition, instead use the
> 'xics' flag. It's equivalent and it will ease the introduction of new
> XIVE-only IRQ backends if needed.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>

Thanks, applied to ppc-for-5.2.

I still kind of want to remove the last vestiges of those
"backends", but I'm unlikely to have time to do so soon.

> ---
>  hw/ppc/spapr_irq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index 80cf1c3d6bb2..d036c8fef519 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -172,7 +172,7 @@ static int spapr_irq_check(SpaprMachineState *spapr, Error **errp)
>           * To cover both and not confuse the OS, add an early failure in
>           * QEMU.
>           */
> -        if (spapr->irq == &spapr_irq_xive) {
> +        if (!spapr->irq->xics) {
>              error_setg(errp, "XIVE-only machines require a POWER9 CPU");
>              return -1;
>          }

-- 
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

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Re: [PATCH v2] spapr/xive: Use the xics flag to check for XIVE-only IRQ backends

[Cédric Le Goater]

On 8/21/20 1:22 AM, David Gibson wrote:
> On Thu, Aug 20, 2020 at 04:01:06PM +0200, Cédric Le Goater wrote:
>> The sPAPR machine has four different IRQ backends, each implementing
>> the XICS or XIVE interrupt mode or both in the case of the 'dual'
>> backend.
>>
>> If a machine is started in P8 compat mode, QEMU should necessarily
>> support the XICS interrupt mode and in that case, the XIVE-only IRQ
>> backend is invalid. Currently, spapr_irq_check() tests the pointer
>> value to the IRQ backend to check for this condition, instead use the
>> 'xics' flag. It's equivalent and it will ease the introduction of new
>> XIVE-only IRQ backends if needed.
>>
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> 
> Thanks, applied to ppc-for-5.2.
> 
> I still kind of want to remove the last vestiges of those
> "backends", but I'm unlikely to have time to do so soon.

What did you have in mind ? 

Move the 'xics' and 'xive' flags directly under the spapr machine ? 
It would add state.

C.
 
> 
>> ---
>>  hw/ppc/spapr_irq.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
>> index 80cf1c3d6bb2..d036c8fef519 100644
>> --- a/hw/ppc/spapr_irq.c
>> +++ b/hw/ppc/spapr_irq.c
>> @@ -172,7 +172,7 @@ static int spapr_irq_check(SpaprMachineState *spapr, Error **errp)
>>           * To cover both and not confuse the OS, add an early failure in
>>           * QEMU.
>>           */
>> -        if (spapr->irq == &spapr_irq_xive) {
>> +        if (!spapr->irq->xics) {
>>              error_setg(errp, "XIVE-only machines require a POWER9 CPU");
>>              return -1;
>>          }
> 

Re: [PATCH v2] spapr/xive: Use the xics flag to check for XIVE-only IRQ backends

[David Gibson]

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On Fri, Aug 21, 2020 at 07:39:34AM +0200, Cédric Le Goater wrote:
> On 8/21/20 1:22 AM, David Gibson wrote:
> > On Thu, Aug 20, 2020 at 04:01:06PM +0200, Cédric Le Goater wrote:
> >> The sPAPR machine has four different IRQ backends, each implementing
> >> the XICS or XIVE interrupt mode or both in the case of the 'dual'
> >> backend.
> >>
> >> If a machine is started in P8 compat mode, QEMU should necessarily
> >> support the XICS interrupt mode and in that case, the XIVE-only IRQ
> >> backend is invalid. Currently, spapr_irq_check() tests the pointer
> >> value to the IRQ backend to check for this condition, instead use the
> >> 'xics' flag. It's equivalent and it will ease the introduction of new
> >> XIVE-only IRQ backends if needed.
> >>
> >> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> > 
> > Thanks, applied to ppc-for-5.2.
> > 
> > I still kind of want to remove the last vestiges of those
> > "backends", but I'm unlikely to have time to do so soon.
> 
> What did you have in mind ? 
> 
> Move the 'xics' and 'xive' flags directly under the spapr machine ? 
> It would add state.

Looking at my draft patches, looks like I was planning to replace the
flags with spapr caps.  IIRC there was migration breakage with my
draft, though, can't remember what would be needed to fix it.

-- 
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

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