* Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
@ 2020-02-15 5:39 Leonardo Bras
2020-02-27 13:29 ` Desnes Augusto Nunes do Rosario
0 siblings, 1 reply; 4+ messages in thread
From: Leonardo Bras @ 2020-02-15 5:39 UTC (permalink / raw)
To: desnesn, linuxppc-dev; +Cc: desnesn, gromero
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Hello Desnes, thanks for the patch.
"Desnes A. Nunes do Rosario" <desnesn@linux.ibm.com> writes:
> PowerVM systems running compatibility mode on a few Power8 revisions are
> still vulnerable to the hardware defect that loses PMU exceptions arriving
> prior to a context switch.
>
> The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
> cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
> compatibility mode systems.
>
> Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
> Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
> ---
> arch/powerpc/kernel/cputable.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
> index e745abc5457a..5bfef6263dfb 100644
> --- a/arch/powerpc/kernel/cputable.c
> +++ b/arch/powerpc/kernel/cputable.c
> @@ -2198,6 +2198,8 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
> if (old.oprofile_cpu_type != NULL) {
> t->oprofile_cpu_type = old.oprofile_cpu_type;
> t->oprofile_type = old.oprofile_type;
> + if (old.cpu_features & CPU_FTR_PMAO_BUG)
> + t->cpu_features |= CPU_FTR_PMAO_BUG;
What are your thoughts about doing:
t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG;
Also, I would recommend adding a short comment on top of the added
lines explaining why it is needed.
Best regards,
Leonardo Bras
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
2020-02-15 5:39 [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems Leonardo Bras
@ 2020-02-27 13:29 ` Desnes Augusto Nunes do Rosario
0 siblings, 0 replies; 4+ messages in thread
From: Desnes Augusto Nunes do Rosario @ 2020-02-27 13:29 UTC (permalink / raw)
To: Leonardo Bras, linuxppc-dev; +Cc: gromero
Hello Leonardo,
On 2/15/20 2:39 AM, Leonardo Bras wrote:
> Hello Desnes, thanks for the patch.
>
> "Desnes A. Nunes do Rosario" <desnesn@linux.ibm.com> writes:
>
>> PowerVM systems running compatibility mode on a few Power8 revisions are
>> still vulnerable to the hardware defect that loses PMU exceptions arriving
>> prior to a context switch.
>>
>> The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
>> cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
>> compatibility mode systems.
>>
>> Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
>> Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
>> ---
>> arch/powerpc/kernel/cputable.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
>> index e745abc5457a..5bfef6263dfb 100644
>> --- a/arch/powerpc/kernel/cputable.c
>> +++ b/arch/powerpc/kernel/cputable.c
>> @@ -2198,6 +2198,8 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
>> if (old.oprofile_cpu_type != NULL) {
>> t->oprofile_cpu_type = old.oprofile_cpu_type;
>> t->oprofile_type = old.oprofile_type;
>> + if (old.cpu_features & CPU_FTR_PMAO_BUG)
>> + t->cpu_features |= CPU_FTR_PMAO_BUG;
> What are your thoughts about doing:
> t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG;
Looks good to me.
> Also, I would recommend adding a short comment on top of the added
> lines explaining why it is needed.
Sure, I'll send a second version.
Thanks for the review.
>
> Best regards,
> Leonardo Bras
>
--
Desnes A. Nunes do Rosario
--------------------------------
Advisory Software Engineer - IBM
Virtual Onsite Engineer - Red Hat
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
@ 2020-02-14 0:19 Desnes A. Nunes do Rosario
2020-02-15 6:26 ` Leonardo Bras
0 siblings, 1 reply; 4+ messages in thread
From: Desnes A. Nunes do Rosario @ 2020-02-14 0:19 UTC (permalink / raw)
To: linuxppc-dev; +Cc: desnesn, gromero
PowerVM systems running compatibility mode on a few Power8 revisions are
still vulnerable to the hardware defect that loses PMU exceptions arriving
prior to a context switch.
The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
compatibility mode systems.
Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
---
arch/powerpc/kernel/cputable.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index e745abc5457a..5bfef6263dfb 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -2198,6 +2198,8 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
if (old.oprofile_cpu_type != NULL) {
t->oprofile_cpu_type = old.oprofile_cpu_type;
t->oprofile_type = old.oprofile_type;
+ if (old.cpu_features & CPU_FTR_PMAO_BUG)
+ t->cpu_features |= CPU_FTR_PMAO_BUG;
}
}
--
2.21.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
2020-02-14 0:19 Desnes A. Nunes do Rosario
@ 2020-02-15 6:26 ` Leonardo Bras
0 siblings, 0 replies; 4+ messages in thread
From: Leonardo Bras @ 2020-02-15 6:26 UTC (permalink / raw)
To: Desnes A. Nunes do Rosario, linuxppc-dev; +Cc: gromero
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Hello Desnes, thanks for the patch.
On Thu, 2020-02-13 at 21:19 -0300, Desnes A. Nunes do Rosario wrote:
> PowerVM systems running compatibility mode on a few Power8 revisions are
> still vulnerable to the hardware defect that loses PMU exceptions arriving
> prior to a context switch.
>
> The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
> cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
> compatibility mode systems.
>
> Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
> Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
> ---
> arch/powerpc/kernel/cputable.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
> index e745abc5457a..5bfef6263dfb 100644
> --- a/arch/powerpc/kernel/cputable.c
> +++ b/arch/powerpc/kernel/cputable.c
> @@ -2198,6 +2198,8 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
> if (old.oprofile_cpu_type != NULL) {
> t->oprofile_cpu_type = old.oprofile_cpu_type;
> t->oprofile_type = old.oprofile_type;
> + if (old.cpu_features & CPU_FTR_PMAO_BUG)
> + t->cpu_features |= CPU_FTR_PMAO_BUG;
> }
> }
>
What are your thoughts about doing:
t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG;
Also, I would recommend adding a short comment on top of the added
lines explaining why it is needed.
Best regards,
Leonardo Bras
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-02-15 5:39 [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems Leonardo Bras
2020-02-27 13:29 ` Desnes Augusto Nunes do Rosario
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2020-02-14 0:19 Desnes A. Nunes do Rosario
2020-02-15 6:26 ` Leonardo Bras
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