[PATCH] arm64: skip cpu nodes marked as disabled in DT

[PATCH] arm64: skip cpu nodes marked as disabled in DT

[Rohit Khanna]

Skip the CPU nodes that are marked as disabled in DT.

Bug 1828570

Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
Reviewed-on: http://git-master/r/1245333
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
---
 arch/arm64/kernel/smp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index f3e2e3aec0b0..2b4371b0948d 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
 	for_each_node_by_type(dn, "cpu") {
 		u64 hwid = of_get_cpu_mpidr(dn);
 
+		/* Check to see if the cpu is disabled */
+		if (!of_device_is_available(dn))
+			goto next;
+
 		if (hwid == INVALID_HWID)
 			goto next;
 
-- 
2.1.4

Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

[Rohit Khanna]

Adding few other folks.

Thanks
Rohit
________________________________________
From: Rohit Khanna
Sent: Wednesday, April 25, 2018 4:08 PM
To: catalin.marinas@arm.com; will.deacon@arm.com
Cc: linux-kernel@vger.kernel.org; Rohit Khanna
Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT

Skip the CPU nodes that are marked as disabled in DT.

Bug 1828570

Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
Reviewed-on: http://git-master/r/1245333
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
---
 arch/arm64/kernel/smp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index f3e2e3aec0b0..2b4371b0948d 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
        for_each_node_by_type(dn, "cpu") {
                u64 hwid = of_get_cpu_mpidr(dn);

+               /* Check to see if the cpu is disabled */
+               if (!of_device_is_available(dn))
+                       goto next;
+
                if (hwid == INVALID_HWID)
                        goto next;

--
2.1.4

Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

[Catalin Marinas]

On Wed, Apr 25, 2018 at 11:36:06PM +0000, Rohit Khanna wrote:
> Adding few other folks.

It looks fine to me but cc'ing Mark and Lorenzo (and it should have been
posted on linux-arm-kernel@lists.infradead.org).

> From: Rohit Khanna
> Sent: Wednesday, April 25, 2018 4:08 PM
> To: catalin.marinas@arm.com; will.deacon@arm.com
> Cc: linux-kernel@vger.kernel.org; Rohit Khanna
> Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT
> 
> Skip the CPU nodes that are marked as disabled in DT.
> 
> Bug 1828570
> 
> Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
> Reviewed-on: http://git-master/r/1245333
> Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
> ---
>  arch/arm64/kernel/smp.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index f3e2e3aec0b0..2b4371b0948d 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
>         for_each_node_by_type(dn, "cpu") {
>                 u64 hwid = of_get_cpu_mpidr(dn);
> 
> +               /* Check to see if the cpu is disabled */
> +               if (!of_device_is_available(dn))
> +                       goto next;
> +
>                 if (hwid == INVALID_HWID)
>                         goto next;
> 
> --
> 2.1.4

Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

[Lorenzo Pieralisi]

On Thu, Apr 26, 2018 at 08:25:14AM +0100, Catalin Marinas wrote:
> On Wed, Apr 25, 2018 at 11:36:06PM +0000, Rohit Khanna wrote:
> > Adding few other folks.
> 
> It looks fine to me but cc'ing Mark and Lorenzo (and it should have been
> posted on linux-arm-kernel@lists.infradead.org).
> 
> > From: Rohit Khanna
> > Sent: Wednesday, April 25, 2018 4:08 PM
> > To: catalin.marinas@arm.com; will.deacon@arm.com
> > Cc: linux-kernel@vger.kernel.org; Rohit Khanna
> > Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT
> > 
> > Skip the CPU nodes that are marked as disabled in DT.
> > 
> > Bug 1828570

That's not information that can be used in its current form, which
bug-tracking system ?

> > Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
> > Reviewed-on: http://git-master/r/1245333

If it is a public mailing list discussion the

Link:

tag and the lkml redirector should be used, I do not know what the
redirector used here is though.

Process is defined here:

https://www.kernel.org/doc/html/latest/process/submitting-patches.html

> > Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
> > ---
> >  arch/arm64/kernel/smp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index f3e2e3aec0b0..2b4371b0948d 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> > @@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
> >         for_each_node_by_type(dn, "cpu") {
> >                 u64 hwid = of_get_cpu_mpidr(dn);
> > 
> > +               /* Check to see if the cpu is disabled */
> > +               if (!of_device_is_available(dn))
> > +                       goto next;
> > +

This was discussed a long time ago and kind of dropped - I digged the
thread out of archives for everyone's information:

http://lists.infradead.org/pipermail/linux-arm-kernel/2013-June/174324.html

Lorenzo

Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

[Rohit Khanna]

Thanks Lorenzo for pulling out the old thread.

So just to make sure my understanding is correct from the discussion on that thread, below is not a preferred approach.

"If CPUs are marked as disabled in the devicetree, make sure they do
not exist in the system CPU information and CPU topology information."


The reason is because - "The meaning of disabled for cpus in ePAPR is that the cpu is offline
(i.e. in a spinloop or wfi), not that the cpu is unavailable."


Preferred approach is -
"Since with this approach the DT should change anyway if on different
>    hardware devices based on the same chip you want to allow booting a
>    different number of CPUs, why do not we remove the cpu nodes instead of
>    disabling them"

Thanks
Rohit
________________________________________
From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Sent: Thursday, April 26, 2018 3:18 AM
To: Catalin Marinas; Rohit Khanna
Cc: will.deacon@arm.com; linux-kernel@vger.kernel.org; Thierry Reding; Alexander Van Brunt; Bo Yan; Jason Sequeira; Mark Rutland
Subject: Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

On Thu, Apr 26, 2018 at 08:25:14AM +0100, Catalin Marinas wrote:
> On Wed, Apr 25, 2018 at 11:36:06PM +0000, Rohit Khanna wrote:
> > Adding few other folks.
>
> It looks fine to me but cc'ing Mark and Lorenzo (and it should have been
> posted on linux-arm-kernel@lists.infradead.org).
>
> > From: Rohit Khanna
> > Sent: Wednesday, April 25, 2018 4:08 PM
> > To: catalin.marinas@arm.com; will.deacon@arm.com
> > Cc: linux-kernel@vger.kernel.org; Rohit Khanna
> > Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT
> >
> > Skip the CPU nodes that are marked as disabled in DT.
> >
> > Bug 1828570

That's not information that can be used in its current form, which
bug-tracking system ?

> > Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
> > Reviewed-on: http://git-master/r/1245333

If it is a public mailing list discussion the

Link:

tag and the lkml redirector should be used, I do not know what the
redirector used here is though.

Process is defined here:

https://www.kernel.org/doc/html/latest/process/submitting-patches.html

> > Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
> > ---
> >  arch/arm64/kernel/smp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index f3e2e3aec0b0..2b4371b0948d 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> > @@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
> >         for_each_node_by_type(dn, "cpu") {
> >                 u64 hwid = of_get_cpu_mpidr(dn);
> >
> > +               /* Check to see if the cpu is disabled */
> > +               if (!of_device_is_available(dn))
> > +                       goto next;
> > +

This was discussed a long time ago and kind of dropped - I digged the
thread out of archives for everyone's information:

http://lists.infradead.org/pipermail/linux-arm-kernel/2013-June/174324.html

Lorenzo

Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT

[Lorenzo Pieralisi]

On Thu, Apr 26, 2018 at 07:54:06PM +0000, Rohit Khanna wrote:
> Thanks Lorenzo for pulling out the old thread.
> 
> So just to make sure my understanding is correct from the discussion
> on that thread, below is not a preferred approach.
> 
> "If CPUs are marked as disabled in the devicetree, make sure they do
> not exist in the system CPU information and CPU topology information."
> 
> 
> The reason is because - "The meaning of disabled for cpus in ePAPR is
> that the cpu is offline (i.e. in a spinloop or wfi), not that the cpu
> is unavailable."
> 
> 
> Preferred approach is -
> "Since with this approach the DT should change anyway if on different
> >    hardware devices based on the same chip you want to allow booting a
> >    different number of CPUs, why do not we remove the cpu nodes instead of
> >    disabling them"

Yes, I think that's the best course of action and it was the outcome
of that email thread.

Lorenzo

> Thanks
> Rohit
> ________________________________________
> From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Sent: Thursday, April 26, 2018 3:18 AM
> To: Catalin Marinas; Rohit Khanna
> Cc: will.deacon@arm.com; linux-kernel@vger.kernel.org; Thierry Reding; Alexander Van Brunt; Bo Yan; Jason Sequeira; Mark Rutland
> Subject: Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT
> 
> On Thu, Apr 26, 2018 at 08:25:14AM +0100, Catalin Marinas wrote:
> > On Wed, Apr 25, 2018 at 11:36:06PM +0000, Rohit Khanna wrote:
> > > Adding few other folks.
> >
> > It looks fine to me but cc'ing Mark and Lorenzo (and it should have been
> > posted on linux-arm-kernel@lists.infradead.org).
> >
> > > From: Rohit Khanna
> > > Sent: Wednesday, April 25, 2018 4:08 PM
> > > To: catalin.marinas@arm.com; will.deacon@arm.com
> > > Cc: linux-kernel@vger.kernel.org; Rohit Khanna
> > > Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT
> > >
> > > Skip the CPU nodes that are marked as disabled in DT.
> > >
> > > Bug 1828570
> 
> That's not information that can be used in its current form, which
> bug-tracking system ?
> 
> > > Signed-off-by: Rohit Khanna <rokhanna@nvidia.com>
> > > Reviewed-on: http://git-master/r/1245333
> 
> If it is a public mailing list discussion the
> 
> Link:
> 
> tag and the lkml redirector should be used, I do not know what the
> redirector used here is though.
> 
> Process is defined here:
> 
> https://www.kernel.org/doc/html/latest/process/submitting-patches.html
> 
> > > Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
> > > ---
> > >  arch/arm64/kernel/smp.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > > index f3e2e3aec0b0..2b4371b0948d 100644
> > > --- a/arch/arm64/kernel/smp.c
> > > +++ b/arch/arm64/kernel/smp.c
> > > @@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void)
> > >         for_each_node_by_type(dn, "cpu") {
> > >                 u64 hwid = of_get_cpu_mpidr(dn);
> > >
> > > +               /* Check to see if the cpu is disabled */
> > > +               if (!of_device_is_available(dn))
> > > +                       goto next;
> > > +
> 
> This was discussed a long time ago and kind of dropped - I digged the
> thread out of archives for everyone's information:
> 
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-June/174324.html
> 
> Lorenzo