| Message ID | 20231009230858.3444834-7-rananta@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU | expand |
On Mon, Oct 09, 2023 at 11:08:52PM +0000, Raghavendra Rao Ananta wrote: > Add a helper, kvm_arm_get_num_counters(), to read the number > of counters from the arm_pmu associated to the VM. Make the > function global as upcoming patches will be interested to > know the value while setting the PMCR.N of the guest from > userspace. > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > --- > arch/arm64/kvm/pmu-emul.c | 17 +++++++++++++++++ > include/kvm/arm_pmu.h | 6 ++++++ > 2 files changed, 23 insertions(+) > > diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c > index a161d6266a5c..84aa8efd9163 100644 > --- a/arch/arm64/kvm/pmu-emul.c > +++ b/arch/arm64/kvm/pmu-emul.c > @@ -873,6 +873,23 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq) > return true; > } > > +/** > + * kvm_arm_get_num_counters - Get the number of general-purpose PMU counters. > + * @kvm: The kvm pointer > + */ > +int kvm_arm_get_num_counters(struct kvm *kvm) nit: the naming suggests this returns the configured number of PMCs, not the limit. Maybe kvm_arm_pmu_get_max_counters()? > +{ > + struct arm_pmu *arm_pmu = kvm->arch.arm_pmu; > + > + lockdep_assert_held(&kvm->arch.config_lock); > + > + /* > + * The arm_pmu->num_events considers the cycle counter as well. > + * Ignore that and return only the general-purpose counters. > + */ > + return arm_pmu->num_events - 1; > +} > + > static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu) > { > lockdep_assert_held(&kvm->arch.config_lock); > diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h > index cd980d78b86b..672f3e9d7eea 100644 > --- a/include/kvm/arm_pmu.h > +++ b/include/kvm/arm_pmu.h > @@ -102,6 +102,7 @@ void kvm_vcpu_pmu_resync_el0(void); > > u8 kvm_arm_pmu_get_pmuver_limit(void); > int kvm_arm_set_default_pmu(struct kvm *kvm); > +int kvm_arm_get_num_counters(struct kvm *kvm); > > u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu); > #else > @@ -181,6 +182,11 @@ static inline int kvm_arm_set_default_pmu(struct kvm *kvm) > return -ENODEV; > } > > +static inline int kvm_arm_get_num_counters(struct kvm *kvm) > +{ > + return -ENODEV; > +} > + > static inline u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu) > { > return 0; > -- > 2.42.0.609.gbb76f46606-goog >
On Tue, Oct 10, 2023 at 10:30:31PM +0000, Oliver Upton wrote: > On Mon, Oct 09, 2023 at 11:08:52PM +0000, Raghavendra Rao Ananta wrote: > > Add a helper, kvm_arm_get_num_counters(), to read the number > > of counters from the arm_pmu associated to the VM. Make the > > function global as upcoming patches will be interested to > > know the value while setting the PMCR.N of the guest from > > userspace. > > > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > > --- > > arch/arm64/kvm/pmu-emul.c | 17 +++++++++++++++++ > > include/kvm/arm_pmu.h | 6 ++++++ > > 2 files changed, 23 insertions(+) > > > > diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c > > index a161d6266a5c..84aa8efd9163 100644 > > --- a/arch/arm64/kvm/pmu-emul.c > > +++ b/arch/arm64/kvm/pmu-emul.c > > @@ -873,6 +873,23 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq) > > return true; > > } > > > > +/** > > + * kvm_arm_get_num_counters - Get the number of general-purpose PMU counters. > > + * @kvm: The kvm pointer > > + */ > > +int kvm_arm_get_num_counters(struct kvm *kvm) > > nit: the naming suggests this returns the configured number of PMCs, not > the limit. > > Maybe kvm_arm_pmu_get_max_counters()? Following up on the matter -- please try to avoid sending patches that add helpers without any users. Lifting *existing* logic into a helper and updating the callsites is itself worthy of a separate patch. But adding a new function called by nobody doesn't do much, and can easily be squashed into the patch that consumes the new logic.
Hi Oliver, On Thu, Oct 12, 2023 at 10:43 PM Oliver Upton <oliver.upton@linux.dev> wrote: > > On Tue, Oct 10, 2023 at 10:30:31PM +0000, Oliver Upton wrote: > > On Mon, Oct 09, 2023 at 11:08:52PM +0000, Raghavendra Rao Ananta wrote: > > > Add a helper, kvm_arm_get_num_counters(), to read the number > > > of counters from the arm_pmu associated to the VM. Make the > > > function global as upcoming patches will be interested to > > > know the value while setting the PMCR.N of the guest from > > > userspace. > > > > > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > > > --- > > > arch/arm64/kvm/pmu-emul.c | 17 +++++++++++++++++ > > > include/kvm/arm_pmu.h | 6 ++++++ > > > 2 files changed, 23 insertions(+) > > > > > > diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c > > > index a161d6266a5c..84aa8efd9163 100644 > > > --- a/arch/arm64/kvm/pmu-emul.c > > > +++ b/arch/arm64/kvm/pmu-emul.c > > > @@ -873,6 +873,23 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq) > > > return true; > > > } > > > > > > +/** > > > + * kvm_arm_get_num_counters - Get the number of general-purpose PMU counters. > > > + * @kvm: The kvm pointer > > > + */ > > > +int kvm_arm_get_num_counters(struct kvm *kvm) > > > > nit: the naming suggests this returns the configured number of PMCs, not > > the limit. > > > > Maybe kvm_arm_pmu_get_max_counters()? > Sure, kvm_arm_pmu_get_max_counters() it is! > Following up on the matter -- please try to avoid sending patches that > add helpers without any users. Lifting *existing* logic into a helper > and updating the callsites is itself worthy of a separate patch. But > adding a new function called by nobody doesn't do much, and can easily > be squashed into the patch that consumes the new logic. > Sounds good. I'll squash patches of this type into the caller patches. Thank you. Raghavendra > -- > Thanks, > Oliver
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index a161d6266a5c..84aa8efd9163 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -873,6 +873,23 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq) return true; } +/** + * kvm_arm_get_num_counters - Get the number of general-purpose PMU counters. + * @kvm: The kvm pointer + */ +int kvm_arm_get_num_counters(struct kvm *kvm) +{ + struct arm_pmu *arm_pmu = kvm->arch.arm_pmu; + + lockdep_assert_held(&kvm->arch.config_lock); + + /* + * The arm_pmu->num_events considers the cycle counter as well. + * Ignore that and return only the general-purpose counters. + */ + return arm_pmu->num_events - 1; +} + static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu) { lockdep_assert_held(&kvm->arch.config_lock); diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h index cd980d78b86b..672f3e9d7eea 100644 --- a/include/kvm/arm_pmu.h +++ b/include/kvm/arm_pmu.h @@ -102,6 +102,7 @@ void kvm_vcpu_pmu_resync_el0(void); u8 kvm_arm_pmu_get_pmuver_limit(void); int kvm_arm_set_default_pmu(struct kvm *kvm); +int kvm_arm_get_num_counters(struct kvm *kvm); u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu); #else @@ -181,6 +182,11 @@ static inline int kvm_arm_set_default_pmu(struct kvm *kvm) return -ENODEV; } +static inline int kvm_arm_get_num_counters(struct kvm *kvm) +{ + return -ENODEV; +} + static inline u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu) { return 0;
Add a helper, kvm_arm_get_num_counters(), to read the number of counters from the arm_pmu associated to the VM. Make the function global as upcoming patches will be interested to know the value while setting the PMCR.N of the guest from userspace. Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> --- arch/arm64/kvm/pmu-emul.c | 17 +++++++++++++++++ include/kvm/arm_pmu.h | 6 ++++++ 2 files changed, 23 insertions(+)