Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
Hello Leonardo,
On 2/15/20 2:39 AM, Leonardo Bras wrote:
Hello Desnes, thanks for the patch.
"Desnes A. Nunes do Rosario" 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
---
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
Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
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
> ---
> 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
signature.asc
Description: This is a digitally signed message part
Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
Hello Desnes, thanks for the patch.
"Desnes A. Nunes do Rosario" 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
> ---
> 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
signature.asc
Description: This is a digitally signed message part
[PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
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
---
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
