* Re: [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-08-31 11:47 [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline Gautham R. Shenoy
@ 2017-08-31 12:07 ` Nicholas Piggin
2017-09-01 10:08 ` Akshay Adiga
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Nicholas Piggin @ 2017-08-31 12:07 UTC (permalink / raw)
To: Gautham R. Shenoy
Cc: Michael Ellerman, Vaidyanathan Srinivasan, Shilpasri G Bhat,
Akshay Adiga, Pavithra Prakash, linuxppc-dev, linux-kernel
On Thu, 31 Aug 2017 17:17:41 +0530
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> an offlined CPU which is in a deep stop state.
>
> In the case where the stop-api support is found to be lacking, the
> commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> states when stop-api fails") disables deep states that lose hypervisor
> context. Thus in this case, the offlined CPU will be put to some
> shallow idle state.
>
> However, we currently unconditionally clear the PECE1 in LPCR via
> stop-api during CPU-Hotplug even when deep states are disabled due to
> stop-api failure.
>
> Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> *only* when the offlined CPU will be put to a deep state that loses
> hypervisor context.
This looks okay to me. The bug is due to calling opal_slw_set_reg when
firmware has not enabled that feature, right?
>
> Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug")
>
> Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> ---
> arch/powerpc/platforms/powernv/idle.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index 9f59041..23f8fba 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -393,7 +393,13 @@ static void pnv_program_cpu_hotplug_lpcr(unsigned int cpu, u64 lpcr_val)
> u64 pir = get_hard_smp_processor_id(cpu);
>
> mtspr(SPRN_LPCR, lpcr_val);
> - opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> +
> + /*
> + * Program the LPCR via stop-api only for deepest stop state
> + * can lose hypervisor context.
> + */
> + if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
> + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> }
>
> /*
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-08-31 11:47 [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline Gautham R. Shenoy
2017-08-31 12:07 ` Nicholas Piggin
@ 2017-09-01 10:08 ` Akshay Adiga
2017-09-01 10:38 ` Nicholas Piggin
2017-09-06 9:02 ` pavrampu
2017-09-21 1:46 ` Michael Ellerman
3 siblings, 1 reply; 7+ messages in thread
From: Akshay Adiga @ 2017-09-01 10:08 UTC (permalink / raw)
To: Nicholas Piggin
Cc: linux-kernel, Shilpasri G Bhat, Pavithra Prakash, linuxppc-dev,
Gautham R. Shenoy
On 08/31/2017 05:37 PM, Nicholas Piggin wrote:
> On Thu, 31 Aug 2017 17:17:41 +0530
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> wrote:
>
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> >
> > commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> > stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> > an offlined CPU which is in a deep stop state.
> >
> > In the case where the stop-api support is found to be lacking, the
> > commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> > states when stop-api fails") disables deep states that lose hypervisor
> > context. Thus in this case, the offlined CPU will be put to some
> > shallow idle state.
> >
> > However, we currently unconditionally clear the PECE1 in LPCR via
> > stop-api during CPU-Hotplug even when deep states are disabled due to
> > stop-api failure.
> >
> > Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> > *only* when the offlined CPU will be put to a deep state that loses
> > hypervisor context.
>
> This looks okay to me. The bug is due to calling opal_slw_set_reg when
> firmware has not enabled that feature, right?
Yes,
In the case where the stop-api support is found to be lacking, the
commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
states when stop-api fails") disables deep states that lose hypervisor
context. Thus in this case, the offlined CPU will be put to some shallow
idle state.
If a shallow state ( < stop4 ) is being chosen for cpu hotplug, then :
1) this opal call is not required.
2) may not be supported.
Hence should call opal_slw_set_reg() only if a deep state chosen for
cpu hotplug.
>
> >
> > Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > stop-api only on Hotplug")
> >
> > Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> > ---
> > arch/powerpc/platforms/powernv/idle.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/platforms/powernv/idle.c
> b/arch/powerpc/platforms/powernv/idle.c
> > index 9f59041..23f8fba 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -393,7 +393,13 @@ static void
> pnv_program_cpu_hotplug_lpcr(unsigned int cpu, u64 lpcr_val)
> > u64 pir = get_hard_smp_processor_id(cpu);
> >
> > mtspr(SPRN_LPCR, lpcr_val);
> > - opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > +
> > + /*
> > + * Program the LPCR via stop-api only for deepest stop state
> > + * can lose hypervisor context.
> > + */
> > + if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
> > + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > }
> >
> > /*
>
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-09-01 10:08 ` Akshay Adiga
@ 2017-09-01 10:38 ` Nicholas Piggin
0 siblings, 0 replies; 7+ messages in thread
From: Nicholas Piggin @ 2017-09-01 10:38 UTC (permalink / raw)
To: Akshay Adiga
Cc: linux-kernel, Shilpasri G Bhat, Pavithra Prakash, linuxppc-dev,
Gautham R. Shenoy
On Fri, 1 Sep 2017 15:38:59 +0530
Akshay Adiga <akshay.adiga@linux.vnet.ibm.com> wrote:
> On 08/31/2017 05:37 PM, Nicholas Piggin wrote:
> > On Thu, 31 Aug 2017 17:17:41 +0530
> > "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> wrote:
> >
> > > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> > >
> > > commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > > stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> > > stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> > > an offlined CPU which is in a deep stop state.
> > >
> > > In the case where the stop-api support is found to be lacking, the
> > > commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> > > states when stop-api fails") disables deep states that lose hypervisor
> > > context. Thus in this case, the offlined CPU will be put to some
> > > shallow idle state.
> > >
> > > However, we currently unconditionally clear the PECE1 in LPCR via
> > > stop-api during CPU-Hotplug even when deep states are disabled due to
> > > stop-api failure.
> > >
> > > Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> > > *only* when the offlined CPU will be put to a deep state that loses
> > > hypervisor context.
> >
> > This looks okay to me. The bug is due to calling opal_slw_set_reg when
> > firmware has not enabled that feature, right?
> Yes,
>
> In the case where the stop-api support is found to be lacking, the
> commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> states when stop-api fails") disables deep states that lose hypervisor
> context. Thus in this case, the offlined CPU will be put to some shallow
> idle state.
>
> If a shallow state ( < stop4 ) is being chosen for cpu hotplug, then :
> 1) this opal call is not required.
> 2) may not be supported.
>
> Hence should call opal_slw_set_reg() only if a deep state chosen for
> cpu hotplug.
That makes sense, thanks for confirming.
> >
> > >
> > > Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > > stop-api only on Hotplug")
> > >
> > > Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> > > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> > > ---
> > > arch/powerpc/platforms/powernv/idle.c | 8 +++++++-
> > > 1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/powerpc/platforms/powernv/idle.c
> > b/arch/powerpc/platforms/powernv/idle.c
> > > index 9f59041..23f8fba 100644
> > > --- a/arch/powerpc/platforms/powernv/idle.c
> > > +++ b/arch/powerpc/platforms/powernv/idle.c
> > > @@ -393,7 +393,13 @@ static void
> > pnv_program_cpu_hotplug_lpcr(unsigned int cpu, u64 lpcr_val)
> > > u64 pir = get_hard_smp_processor_id(cpu);
> > >
> > > mtspr(SPRN_LPCR, lpcr_val);
> > > - opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > > +
> > > + /*
> > > + * Program the LPCR via stop-api only for deepest stop state
> > > + * can lose hypervisor context.
> > > + */
> > > + if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
> > > + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > > }
> > >
> > > /*
> >
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-08-31 11:47 [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline Gautham R. Shenoy
2017-08-31 12:07 ` Nicholas Piggin
2017-09-01 10:08 ` Akshay Adiga
@ 2017-09-06 9:02 ` pavrampu
2017-09-19 14:32 ` Akshay Adiga
2017-09-21 1:46 ` Michael Ellerman
3 siblings, 1 reply; 7+ messages in thread
From: pavrampu @ 2017-09-06 9:02 UTC (permalink / raw)
To: Gautham R. Shenoy
Cc: Michael Ellerman, Nicholas Piggin, Vaidyanathan Srinivasan,
Shilpasri G Bhat, Akshay Adiga, Pavithra Prakash, linuxppc-dev,
linux-kernel
On 2017-08-31 17:17, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> an offlined CPU which is in a deep stop state.
>
> In the case where the stop-api support is found to be lacking, the
> commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> states when stop-api fails") disables deep states that lose hypervisor
> context. Thus in this case, the offlined CPU will be put to some
> shallow idle state.
>
> However, we currently unconditionally clear the PECE1 in LPCR via
> stop-api during CPU-Hotplug even when deep states are disabled due to
> stop-api failure.
>
> Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> *only* when the offlined CPU will be put to a deep state that loses
> hypervisor context.
>
> Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug")
>
> Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Tested-by: Pavithra Prakash <pavrampu@linux.vnet.ibm.com>
> ---
> arch/powerpc/platforms/powernv/idle.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/idle.c
> b/arch/powerpc/platforms/powernv/idle.c
> index 9f59041..23f8fba 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -393,7 +393,13 @@ static void pnv_program_cpu_hotplug_lpcr(unsigned
> int cpu, u64 lpcr_val)
> u64 pir = get_hard_smp_processor_id(cpu);
>
> mtspr(SPRN_LPCR, lpcr_val);
> - opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> +
> + /*
> + * Program the LPCR via stop-api only for deepest stop state
> + * can lose hypervisor context.
> + */
> + if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
> + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> }
>
> /*
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-09-06 9:02 ` pavrampu
@ 2017-09-19 14:32 ` Akshay Adiga
0 siblings, 0 replies; 7+ messages in thread
From: Akshay Adiga @ 2017-09-19 14:32 UTC (permalink / raw)
To: Michael Ellerman
Cc: Nicholas Piggin, Vaidyanathan Srinivasan, Shilpasri G Bhat,
linuxppc-dev, linux-kernel, Gautham R. Shenoy, pavrampu
Hi Michael,
Any comments on this patch ?
On 09/06/2017 02:32 PM, pavrampu wrote:
> On 2017-08-31 17:17, Gautham R. Shenoy wrote:
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> >
> > commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> > stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> > an offlined CPU which is in a deep stop state.
> >
> > In the case where the stop-api support is found to be lacking, the
> > commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> > states when stop-api fails") disables deep states that lose hypervisor
> > context. Thus in this case, the offlined CPU will be put to some
> > shallow idle state.
> >
> > However, we currently unconditionally clear the PECE1 in LPCR via
> > stop-api during CPU-Hotplug even when deep states are disabled due to
> > stop-api failure.
> >
> > Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> > *only* when the offlined CPU will be put to a deep state that loses
> > hypervisor context.
> >
> > Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> > stop-api only on Hotplug")
> >
> > Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
>
> Tested-by: Pavithra Prakash <pavrampu@linux.vnet.ibm.com>
>
> > ---
> > arch/powerpc/platforms/powernv/idle.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/platforms/powernv/idle.c
> > b/arch/powerpc/platforms/powernv/idle.c
> > index 9f59041..23f8fba 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -393,7 +393,13 @@ static void pnv_program_cpu_hotplug_lpcr(unsigned
> > int cpu, u64 lpcr_val)
> > u64 pir = get_hard_smp_processor_id(cpu);
> >
> > mtspr(SPRN_LPCR, lpcr_val);
> > - opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > +
> > + /*
> > + * Program the LPCR via stop-api only for deepest stop state
> > + * can lose hypervisor context.
> > + */
> > + if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
> > + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> > }
> >
> > /*
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline
2017-08-31 11:47 [PATCH] powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline Gautham R. Shenoy
` (2 preceding siblings ...)
2017-09-06 9:02 ` pavrampu
@ 2017-09-21 1:46 ` Michael Ellerman
3 siblings, 0 replies; 7+ messages in thread
From: Michael Ellerman @ 2017-09-21 1:46 UTC (permalink / raw)
To: Gautham R. Shenoy, Nicholas Piggin, Vaidyanathan Srinivasan,
Shilpasri G Bhat, Akshay Adiga, Pavithra Prakash
Cc: Gautham R. Shenoy, linuxppc-dev, linux-kernel
On Thu, 2017-08-31 at 11:47:41 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> an offlined CPU which is in a deep stop state.
>
> In the case where the stop-api support is found to be lacking, the
> commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> states when stop-api fails") disables deep states that lose hypervisor
> context. Thus in this case, the offlined CPU will be put to some
> shallow idle state.
>
> However, we currently unconditionally clear the PECE1 in LPCR via
> stop-api during CPU-Hotplug even when deep states are disabled due to
> stop-api failure.
>
> Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> *only* when the offlined CPU will be put to a deep state that loses
> hypervisor context.
>
> Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug")
>
> Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> Tested-by: Pavithra Prakash <pavrampu@linux.vnet.ibm.com>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/5d298baa41883fc421acfd932799c0
cheers
^ permalink raw reply [flat|nested] 7+ messages in thread