| Message ID | 20210414134409.1266357-2-maz@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | perf: oprofile spring cleanup | expand |
Hi Marc, On 2021/4/14 21:44, Marc Zyngier wrote: > KVM/arm64 is the sole user of perf_num_counters(), and really > could do without it. Stop using the obsolete API by relying on > the existing probing code. > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > arch/arm64/kvm/perf.c | 7 +------ > arch/arm64/kvm/pmu-emul.c | 2 +- > include/kvm/arm_pmu.h | 4 ++++ > 3 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c > index 739164324afe..b8b398670ef2 100644 > --- a/arch/arm64/kvm/perf.c > +++ b/arch/arm64/kvm/perf.c > @@ -50,12 +50,7 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = { > > int kvm_perf_init(void) > { > - /* > - * Check if HW_PERF_EVENTS are supported by checking the number of > - * hardware performance counters. This could ensure the presence of > - * a physical PMU and CONFIG_PERF_EVENT is selected. > - */ > - if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) > + if (kvm_pmu_probe_pmuver() != 0xf) The probe() function may be called many times (kvm_arm_pmu_v3_set_attr also calls it). I don't know whether the first calling is enough. If so, can we use a static variable in it, so the following calling can return the result right away? Thanks, Keqian
Hi Marc, On 2021/4/15 18:42, Marc Zyngier wrote: > On Thu, 15 Apr 2021 07:59:26 +0100, > Keqian Zhu <zhukeqian1@huawei.com> wrote: >> >> Hi Marc, >> >> On 2021/4/14 21:44, Marc Zyngier wrote: >>> KVM/arm64 is the sole user of perf_num_counters(), and really >>> could do without it. Stop using the obsolete API by relying on >>> the existing probing code. >>> >>> Signed-off-by: Marc Zyngier <maz@kernel.org> >>> --- >>> arch/arm64/kvm/perf.c | 7 +------ >>> arch/arm64/kvm/pmu-emul.c | 2 +- >>> include/kvm/arm_pmu.h | 4 ++++ >>> 3 files changed, 6 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c >>> index 739164324afe..b8b398670ef2 100644 >>> --- a/arch/arm64/kvm/perf.c >>> +++ b/arch/arm64/kvm/perf.c >>> @@ -50,12 +50,7 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = { >>> >>> int kvm_perf_init(void) >>> { >>> - /* >>> - * Check if HW_PERF_EVENTS are supported by checking the number of >>> - * hardware performance counters. This could ensure the presence of >>> - * a physical PMU and CONFIG_PERF_EVENT is selected. >>> - */ >>> - if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) >>> + if (kvm_pmu_probe_pmuver() != 0xf) >> The probe() function may be called many times >> (kvm_arm_pmu_v3_set_attr also calls it). I don't know whether the >> first calling is enough. If so, can we use a static variable in it, >> so the following calling can return the result right away? > > No, because that wouldn't help with crappy big-little implementations > that could have PMUs with different versions. We want to find the > version at the point where the virtual PMU is created, which is why we > call the probe function once per vcpu. I see. But AFAICS the pmuver is placed in kvm->arch, and the probe function is called once per VM. Maybe I miss something. > > This of course is broken in other ways (BL+KVM is a total disaster > when it comes to PMU), but making this static would just make it > worse. OK. Thanks, Keqian
On Wed, Apr 14, 2021 at 02:44:05PM +0100, Marc Zyngier wrote: > KVM/arm64 is the sole user of perf_num_counters(), and really > could do without it. Stop using the obsolete API by relying on > the existing probing code. > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > arch/arm64/kvm/perf.c | 7 +------ > arch/arm64/kvm/pmu-emul.c | 2 +- > include/kvm/arm_pmu.h | 4 ++++ > 3 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c > index 739164324afe..b8b398670ef2 100644 > --- a/arch/arm64/kvm/perf.c > +++ b/arch/arm64/kvm/perf.c > @@ -50,12 +50,7 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = { > > int kvm_perf_init(void) > { > - /* > - * Check if HW_PERF_EVENTS are supported by checking the number of > - * hardware performance counters. This could ensure the presence of > - * a physical PMU and CONFIG_PERF_EVENT is selected. > - */ > - if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) > + if (kvm_pmu_probe_pmuver() != 0xf) Took me a while to figure out that this returns 0xf if the hardware has a PMUVer of 0x0, so it's all good: Acked-by: Will Deacon <will@kernel.org> Will
diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c index 739164324afe..b8b398670ef2 100644 --- a/arch/arm64/kvm/perf.c +++ b/arch/arm64/kvm/perf.c @@ -50,12 +50,7 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = { int kvm_perf_init(void) { - /* - * Check if HW_PERF_EVENTS are supported by checking the number of - * hardware performance counters. This could ensure the presence of - * a physical PMU and CONFIG_PERF_EVENT is selected. - */ - if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) + if (kvm_pmu_probe_pmuver() != 0xf) static_branch_enable(&kvm_arm_pmu_available); return perf_register_guest_info_callbacks(&kvm_guest_cbs); diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index e32c6e139a09..fd167d4f4215 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -739,7 +739,7 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data, kvm_pmu_create_perf_event(vcpu, select_idx); } -static int kvm_pmu_probe_pmuver(void) +int kvm_pmu_probe_pmuver(void) { struct perf_event_attr attr = { }; struct perf_event *event; diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h index 6fd3cda608e4..864b9997efb2 100644 --- a/include/kvm/arm_pmu.h +++ b/include/kvm/arm_pmu.h @@ -61,6 +61,7 @@ int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu, int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr); int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu); +int kvm_pmu_probe_pmuver(void); #else struct kvm_pmu { }; @@ -116,6 +117,9 @@ static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1) { return 0; } + +static inline int kvm_pmu_probe_pmuver(void) { return 0xf; } + #endif #endif
KVM/arm64 is the sole user of perf_num_counters(), and really could do without it. Stop using the obsolete API by relying on the existing probing code. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kvm/perf.c | 7 +------ arch/arm64/kvm/pmu-emul.c | 2 +- include/kvm/arm_pmu.h | 4 ++++ 3 files changed, 6 insertions(+), 7 deletions(-)