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[PATCH] spapr/xive: Use xive_source_esb_len()

Greg Kurz posted 1 patch 3 years, 8 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/159733969034.320580.6571451425779179477.stgit@bahia.lan
Maintainers: David Gibson <david@gibson.dropbear.id.au>, "Cédric Le Goater" <clg@kaod.org>
hw/intc/spapr_xive.c     |    2 +-
hw/intc/spapr_xive_kvm.c |    2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
[PATCH] spapr/xive: Use xive_source_esb_len()
Posted by Greg Kurz 3 years, 8 months ago 
static inline size_t xive_source_esb_len(XiveSource *xsrc)
{
    return (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
}

Signed-off-by: Greg Kurz <groug@kaod.org>
---
Follow-up on "ppc/xive: Rework setup of XiveSource::esb_mmio"
http://patchwork.ozlabs.org/project/qemu-devel/patch/159679992680.876294.7520540158586170894.stgit@bahia.lan/
---
 hw/intc/spapr_xive.c     |    2 +-
 hw/intc/spapr_xive_kvm.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
index 3c84f64dc464..4bd0d606ba17 100644
--- a/hw/intc/spapr_xive.c
+++ b/hw/intc/spapr_xive.c
@@ -336,7 +336,7 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
     sysbus_init_mmio(SYS_BUS_DEVICE(xive), &end_xsrc->esb_mmio);
 
     /* Set the mapping address of the END ESB pages after the source ESBs */
-    xive->end_base = xive->vc_base + (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
+    xive->end_base = xive->vc_base + xive_source_esb_len(xsrc);
 
     /*
      * Allocate the routing tables
diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
index 82a6f99f022d..3263b982239a 100644
--- a/hw/intc/spapr_xive_kvm.c
+++ b/hw/intc/spapr_xive_kvm.c
@@ -831,7 +831,7 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
 
     /* Clear the KVM mapping */
     xsrc = &xive->source;
-    esb_len = (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
+    esb_len = xive_source_esb_len(xsrc);
 
     if (xsrc->esb_mmap) {
         memory_region_del_subregion(&xsrc->esb_mmio, &xsrc->esb_mmio_kvm);
Re: [PATCH] spapr/xive: Use xive_source_esb_len()
Posted by Gustavo Romero 3 years, 8 months ago 
Hi Greg,

On 8/13/20 2:28 PM, Greg Kurz wrote:
> static inline size_t xive_source_esb_len(XiveSource *xsrc)
> {
>      return (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> }
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
> Follow-up on "ppc/xive: Rework setup of XiveSource::esb_mmio"
> http://patchwork.ozlabs.org/project/qemu-devel/patch/159679992680.876294.7520540158586170894.stgit@bahia.lan/
> ---
>   hw/intc/spapr_xive.c     |    2 +-
>   hw/intc/spapr_xive_kvm.c |    2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index 3c84f64dc464..4bd0d606ba17 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -336,7 +336,7 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
>       sysbus_init_mmio(SYS_BUS_DEVICE(xive), &end_xsrc->esb_mmio);
>   
>       /* Set the mapping address of the END ESB pages after the source ESBs */
> -    xive->end_base = xive->vc_base + (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> +    xive->end_base = xive->vc_base + xive_source_esb_len(xsrc);
>   
>       /*
>        * Allocate the routing tables
> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> index 82a6f99f022d..3263b982239a 100644
> --- a/hw/intc/spapr_xive_kvm.c
> +++ b/hw/intc/spapr_xive_kvm.c
> @@ -831,7 +831,7 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
>   
>       /* Clear the KVM mapping */
>       xsrc = &xive->source;
> -    esb_len = (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> +    esb_len = xive_source_esb_len(xsrc);

hrm I'd like to not add another level of indirection here.
In this specific case I think it's more clear to read just

1ull << xsrc->esb_shift) * xsrc->nr_irqs

and get the idea of one IRQ per ESB page (or pair of pages,
for trigger and management), than one having to look at
what is inside "a box" called xive_source_esb_len().

Wrapping it under another function doesn't help more when
reading the code, XIVE is already tricky enough :)


Cheers,
Gustavo

PS: It seems something messed up with the commit message. It
can be that the ML did that tho...
Re: [PATCH] spapr/xive: Use xive_source_esb_len()
Posted by Greg Kurz 3 years, 8 months ago 
On Thu, 13 Aug 2020 17:38:59 -0300
Gustavo Romero <gromero@linux.vnet.ibm.com> wrote:

> Hi Greg,
> 

Hi Gustavo,

> On 8/13/20 2:28 PM, Greg Kurz wrote:
> > static inline size_t xive_source_esb_len(XiveSource *xsrc)
> > {
> >      return (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > }
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > ---
> > Follow-up on "ppc/xive: Rework setup of XiveSource::esb_mmio"
> > http://patchwork.ozlabs.org/project/qemu-devel/patch/159679992680.876294.7520540158586170894.stgit@bahia.lan/
> > ---
> >   hw/intc/spapr_xive.c     |    2 +-
> >   hw/intc/spapr_xive_kvm.c |    2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> > index 3c84f64dc464..4bd0d606ba17 100644
> > --- a/hw/intc/spapr_xive.c
> > +++ b/hw/intc/spapr_xive.c
> > @@ -336,7 +336,7 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
> >       sysbus_init_mmio(SYS_BUS_DEVICE(xive), &end_xsrc->esb_mmio);
> >   
> >       /* Set the mapping address of the END ESB pages after the source ESBs */
> > -    xive->end_base = xive->vc_base + (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > +    xive->end_base = xive->vc_base + xive_source_esb_len(xsrc);
> >   
> >       /*
> >        * Allocate the routing tables
> > diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> > index 82a6f99f022d..3263b982239a 100644
> > --- a/hw/intc/spapr_xive_kvm.c
> > +++ b/hw/intc/spapr_xive_kvm.c
> > @@ -831,7 +831,7 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
> >   
> >       /* Clear the KVM mapping */
> >       xsrc = &xive->source;
> > -    esb_len = (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > +    esb_len = xive_source_esb_len(xsrc);
> 
> hrm I'd like to not add another level of indirection here.
> In this specific case I think it's more clear to read just
> 
> 1ull << xsrc->esb_shift) * xsrc->nr_irqs
> 
> and get the idea of one IRQ per ESB page (or pair of pages,
> for trigger and management), than one having to look at
> what is inside "a box" called xive_source_esb_len().
> 
> Wrapping it under another function doesn't help more when
> reading the code, XIVE is already tricky enough :)
> 

Heh, XIVE is tricky enough that only a few people will dare
to touch this code and they'd better already know about the
one IRQ per ESB page thingy ;-)

More seriously, this is a matter of taste, but since you're likely
to be involved in XIVE a bit more than me, I'm perfectly fine with
keeping this open-coded.

> 
> Cheers,
> Gustavo
> 
> PS: It seems something messed up with the commit message. It
> can be that the ML did that tho...

It's more laziness on my side... I should have come up with a
proper changelog like "We already have an helper that provides
the length of the ESB mapping. No need to open-code this again."
instead of pasting a code snippet. Time to go on vacation I guess :)

Cheers,

--
Greg
Re: [PATCH] spapr/xive: Use xive_source_esb_len()
Posted by Gustavo Romero 3 years, 8 months ago 
On 8/13/20 7:00 PM, Greg Kurz wrote:
> On Thu, 13 Aug 2020 17:38:59 -0300
> Gustavo Romero <gromero@linux.vnet.ibm.com> wrote:
> 
>> Hi Greg,
>>
> 
> Hi Gustavo,
> 
>> On 8/13/20 2:28 PM, Greg Kurz wrote:
>>> static inline size_t xive_source_esb_len(XiveSource *xsrc)
>>> {
>>>       return (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
>>> }
>>>
>>> Signed-off-by: Greg Kurz <groug@kaod.org>
>>> ---
>>> Follow-up on "ppc/xive: Rework setup of XiveSource::esb_mmio"
>>> http://patchwork.ozlabs.org/project/qemu-devel/patch/159679992680.876294.7520540158586170894.stgit@bahia.lan/
>>> ---
>>>    hw/intc/spapr_xive.c     |    2 +-
>>>    hw/intc/spapr_xive_kvm.c |    2 +-
>>>    2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
>>> index 3c84f64dc464..4bd0d606ba17 100644
>>> --- a/hw/intc/spapr_xive.c
>>> +++ b/hw/intc/spapr_xive.c
>>> @@ -336,7 +336,7 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
>>>        sysbus_init_mmio(SYS_BUS_DEVICE(xive), &end_xsrc->esb_mmio);
>>>    
>>>        /* Set the mapping address of the END ESB pages after the source ESBs */
>>> -    xive->end_base = xive->vc_base + (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
>>> +    xive->end_base = xive->vc_base + xive_source_esb_len(xsrc);
>>>    
>>>        /*
>>>         * Allocate the routing tables
>>> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
>>> index 82a6f99f022d..3263b982239a 100644
>>> --- a/hw/intc/spapr_xive_kvm.c
>>> +++ b/hw/intc/spapr_xive_kvm.c
>>> @@ -831,7 +831,7 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
>>>    
>>>        /* Clear the KVM mapping */
>>>        xsrc = &xive->source;
>>> -    esb_len = (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
>>> +    esb_len = xive_source_esb_len(xsrc);
>>
>> hrm I'd like to not add another level of indirection here.
>> In this specific case I think it's more clear to read just
>>
>> 1ull << xsrc->esb_shift) * xsrc->nr_irqs
>>
>> and get the idea of one IRQ per ESB page (or pair of pages,
>> for trigger and management), than one having to look at
>> what is inside "a box" called xive_source_esb_len().
>>
>> Wrapping it under another function doesn't help more when
>> reading the code, XIVE is already tricky enough :)
>>
> 
> Heh, XIVE is tricky enough that only a few people will dare
> to touch this code and they'd better already know about the
> one IRQ per ESB page thingy ;-)

Yea, maybe someday we get a cool documentation on it.

Luckily I came after Benh and Cédric and took some good info from
OPAL and QEMU code. I found out recently that XIVE support was
merged into FreeBSD and with that it also came some good comments
about xive...


> More seriously, this is a matter of taste, but since you're likely
> to be involved in XIVE a bit more than me, I'm perfectly fine with
> keeping this open-coded.

Thanks, Greg.

Hope there is still some time to enjoy the summer over there :)


Cheers,
Gustavo
Re: [PATCH] spapr/xive: Use xive_source_esb_len()
Posted by Cédric Le Goater 3 years, 8 months ago 
> I found out recently that XIVE support was
> merged into FreeBSD and with that it also came some good comments
> about xive...

cool ! Does it run in a QEMU PowerNV machine ? 

C.
Re: [PATCH] spapr/xive: Use xive_source_esb_len()
Posted by David Gibson 3 years, 8 months ago 
On Thu, Aug 13, 2020 at 05:38:59PM -0300, Gustavo Romero wrote:
> Hi Greg,
> 
> On 8/13/20 2:28 PM, Greg Kurz wrote:
> > static inline size_t xive_source_esb_len(XiveSource *xsrc)
> > {
> >      return (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > }
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > ---
> > Follow-up on "ppc/xive: Rework setup of XiveSource::esb_mmio"
> > http://patchwork.ozlabs.org/project/qemu-devel/patch/159679992680.876294.7520540158586170894.stgit@bahia.lan/
> > ---
> >   hw/intc/spapr_xive.c     |    2 +-
> >   hw/intc/spapr_xive_kvm.c |    2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> > index 3c84f64dc464..4bd0d606ba17 100644
> > --- a/hw/intc/spapr_xive.c
> > +++ b/hw/intc/spapr_xive.c
> > @@ -336,7 +336,7 @@ static void spapr_xive_realize(DeviceState *dev, Error **errp)
> >       sysbus_init_mmio(SYS_BUS_DEVICE(xive), &end_xsrc->esb_mmio);
> >       /* Set the mapping address of the END ESB pages after the source ESBs */
> > -    xive->end_base = xive->vc_base + (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > +    xive->end_base = xive->vc_base + xive_source_esb_len(xsrc);
> >       /*
> >        * Allocate the routing tables
> > diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> > index 82a6f99f022d..3263b982239a 100644
> > --- a/hw/intc/spapr_xive_kvm.c
> > +++ b/hw/intc/spapr_xive_kvm.c
> > @@ -831,7 +831,7 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
> >       /* Clear the KVM mapping */
> >       xsrc = &xive->source;
> > -    esb_len = (1ull << xsrc->esb_shift) * xsrc->nr_irqs;
> > +    esb_len = xive_source_esb_len(xsrc);
> 
> hrm I'd like to not add another level of indirection here.
> In this specific case I think it's more clear to read just
> 
> 1ull << xsrc->esb_shift) * xsrc->nr_irqs
> 
> and get the idea of one IRQ per ESB page (or pair of pages,
> for trigger and management), than one having to look at
> what is inside "a box" called xive_source_esb_len().
> 
> Wrapping it under another function doesn't help more when
> reading the code, XIVE is already tricky enough :)

Given that we're already using it in some places, I'd prefer to use it
in all the places that it's correct to do so.

Applied to ppc-for-5.2.

-- 
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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