[PATCH v3] arm64: perf: Ignore exclude_hv when kernel is running in HYP

[PATCH v3] arm64: perf: Ignore exclude_hv when kernel is running in HYP

[Ganapatrao Kulkarni]

commit d98ecdaca296 ("arm64: perf: Count EL2 events if the kernel is
running in HYP") returns -EINVAL when perf system call perf_event_open is
called with exclude_hv != exclude_kernel. This change breaks applications
on VHE enabled ARMv8.1 platforms. The issue was observed with HHVM
application, which calls perf_event_open with exclude_hv = 1 and
exclude_kernel = 0.

There is no separate hypervisor privilege level when VHE is enabled, the
host kernel runs at EL2. So when VHE is enabled, we should ignore
exclude_hv from the application. This behaviour is consistent with PowerPC
where the exclude_hv is ignored when the hypervisor is not present and with
x86 where this flag is ignored.

Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
---

Changelog:

V2/V3:
 - Changes as per Will Deacon's suggestions.

V1: Initial patch

 arch/arm64/kernel/perf_event.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 57ae9d9..f6748c0 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -871,15 +871,17 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
 
 	if (attr->exclude_idle)
 		return -EPERM;
-	if (is_kernel_in_hyp_mode() &&
-	    attr->exclude_kernel != attr->exclude_hv)
-		return -EINVAL;
+	if (is_kernel_in_hyp_mode()) {
+		if (!attr->exclude_kernel)
+			config_base |= ARMV8_PMU_INCLUDE_EL2;
+	} else {
+		if (attr->exclude_kernel)
+			config_base |= ARMV8_PMU_EXCLUDE_EL1;
+		if (!attr->exclude_hv)
+			config_base |= ARMV8_PMU_INCLUDE_EL2;
+	}
 	if (attr->exclude_user)
 		config_base |= ARMV8_PMU_EXCLUDE_EL0;
-	if (!is_kernel_in_hyp_mode() && attr->exclude_kernel)
-		config_base |= ARMV8_PMU_EXCLUDE_EL1;
-	if (!attr->exclude_hv)
-		config_base |= ARMV8_PMU_INCLUDE_EL2;
 
 	/*
 	 * Install the filter into config_base as this is used to
-- 
1.8.1.4

Re: [PATCH v3] arm64: perf: Ignore exclude_hv when kernel is running in HYP

[Ganapatrao Kulkarni]

Hi Will,

if this patch looks good, can it go in 4.12-rc2 as bug fix?
or can it be queued for 4.13?

On Tue, May 2, 2017 at 9:59 PM, Ganapatrao Kulkarni
<ganapatrao.kulkarni@cavium.com> wrote:
> commit d98ecdaca296 ("arm64: perf: Count EL2 events if the kernel is
> running in HYP") returns -EINVAL when perf system call perf_event_open is
> called with exclude_hv != exclude_kernel. This change breaks applications
> on VHE enabled ARMv8.1 platforms. The issue was observed with HHVM
> application, which calls perf_event_open with exclude_hv = 1 and
> exclude_kernel = 0.
>
> There is no separate hypervisor privilege level when VHE is enabled, the
> host kernel runs at EL2. So when VHE is enabled, we should ignore
> exclude_hv from the application. This behaviour is consistent with PowerPC
> where the exclude_hv is ignored when the hypervisor is not present and with
> x86 where this flag is ignored.
>
> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
> ---
>
> Changelog:
>
> V2/V3:
>  - Changes as per Will Deacon's suggestions.
>
> V1: Initial patch
>
>  arch/arm64/kernel/perf_event.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index 57ae9d9..f6748c0 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -871,15 +871,17 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
>
>         if (attr->exclude_idle)
>                 return -EPERM;
> -       if (is_kernel_in_hyp_mode() &&
> -           attr->exclude_kernel != attr->exclude_hv)
> -               return -EINVAL;
> +       if (is_kernel_in_hyp_mode()) {
> +               if (!attr->exclude_kernel)
> +                       config_base |= ARMV8_PMU_INCLUDE_EL2;
> +       } else {
> +               if (attr->exclude_kernel)
> +                       config_base |= ARMV8_PMU_EXCLUDE_EL1;
> +               if (!attr->exclude_hv)
> +                       config_base |= ARMV8_PMU_INCLUDE_EL2;
> +       }
>         if (attr->exclude_user)
>                 config_base |= ARMV8_PMU_EXCLUDE_EL0;
> -       if (!is_kernel_in_hyp_mode() && attr->exclude_kernel)
> -               config_base |= ARMV8_PMU_EXCLUDE_EL1;
> -       if (!attr->exclude_hv)
> -               config_base |= ARMV8_PMU_INCLUDE_EL2;
>
>         /*
>          * Install the filter into config_base as this is used to
> --
> 1.8.1.4
>

thanks
Ganapat