2023-11-29 07:27:48

by Shaoqin Huang

Subject: [PATCH v2 3/5] KVM: selftests: aarch64: Fix the buggy [enable|disable]_counter

In general, the set/clr registers should always be used in their
write form, never in a RMW form (imagine an interrupt disabling
a counter between the read and the write...).

The current implementation of [enable|disable]_counter both use the RMW
form, fix them by directly write to the set/clr registers.

At the same time, it also fix the buggy disable_counter() which would
end up disabling all the counters.

Signed-off-by: Shaoqin Huang <[email protected]>
---
tools/testing/selftests/kvm/include/aarch64/vpmu.h | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/aarch64/vpmu.h b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
index e0cc1ca1c4b7..644dae3814b5 100644
--- a/tools/testing/selftests/kvm/include/aarch64/vpmu.h
+++ b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
@@ -78,17 +78,13 @@ static inline void write_sel_evtyper(int sel, unsigned long val)

static inline void enable_counter(int idx)
{
- uint64_t v = read_sysreg(pmcntenset_el0);
-
- write_sysreg(BIT(idx) | v, pmcntenset_el0);
+ write_sysreg(BIT(idx), pmcntenset_el0);
isb();
}

static inline void disable_counter(int idx)
{
- uint64_t v = read_sysreg(pmcntenset_el0);
-
- write_sysreg(BIT(idx) | v, pmcntenclr_el0);
+ write_sysreg(BIT(idx), pmcntenclr_el0);
isb();
}

--
2.40.1

2023-12-14 10:13:58

by Eric Auger

Subject: Re: [PATCH v2 3/5] KVM: selftests: aarch64: Fix the buggy [enable|disable]_counter

Hi Shaoqin,

On 11/29/23 08:27, Shaoqin Huang wrote:
> In general, the set/clr registers should always be used in their
> write form, never in a RMW form (imagine an interrupt disabling
> a counter between the read and the write...).
>
> The current implementation of [enable|disable]_counter both use the RMW
> form, fix them by directly write to the set/clr registers.
>
> At the same time, it also fix the buggy disable_counter() which would
> end up disabling all the counters.
>
> Signed-off-by: Shaoqin Huang <[email protected]>
Reviewed-by: Eric Auger <[email protected]>

Eric

> ---
> tools/testing/selftests/kvm/include/aarch64/vpmu.h | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/aarch64/vpmu.h b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
> index e0cc1ca1c4b7..644dae3814b5 100644
> --- a/tools/testing/selftests/kvm/include/aarch64/vpmu.h
> +++ b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
> @@ -78,17 +78,13 @@ static inline void write_sel_evtyper(int sel, unsigned long val)
>
> static inline void enable_counter(int idx)
> {
> - uint64_t v = read_sysreg(pmcntenset_el0);
> -
> - write_sysreg(BIT(idx) | v, pmcntenset_el0);
> + write_sysreg(BIT(idx), pmcntenset_el0);
> isb();
> }
>
> static inline void disable_counter(int idx)
> {
> - uint64_t v = read_sysreg(pmcntenset_el0);
> -
> - write_sysreg(BIT(idx) | v, pmcntenclr_el0);
> + write_sysreg(BIT(idx), pmcntenclr_el0);
> isb();
> }
>