PAPR hypervisor has introduced three new counters in the VPA area of
LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
for context switches from host to guest and vice versa, and 1 counter
for getting the total time spent inside the KVM guest. Add a tracepoint
that enables reading the counters for use by ftrace/perf. Note that this
tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
[1] Terminology:
a. L1 refers to the VM (LPAR) booted on top of PAPR hypervisor
b. L2 refers to the KVM guest booted on top of L1.
Signed-off-by: Vaibhav Jain <[email protected]>
Signed-off-by: Gautam Menghani <[email protected]>
---
v5 -> v6:
1. Use TRACE_EVENT_FN to enable/disable counters only once.
2. Remove the agg. counters from vcpu->arch.
3. Use PACA to maintain old counter values instead of zeroing on every
entry.
4. Simplify variable names
v4 -> v5:
1. Define helper functions for getting/setting the accumulation counter
in L2's VPA
v3 -> v4:
1. After vcpu_run, check the VPA flag instead of checking for tracepoint
being enabled for disabling the cs time accumulation.
v2 -> v3:
1. Move the counter disabling and zeroing code to a different function.
2. Move the get_lppaca() inside the tracepoint_enabled() branch.
3. Add the aggregation logic to maintain total context switch time.
v1 -> v2:
1. Fix the build error due to invalid struct member reference.
arch/powerpc/include/asm/lppaca.h | 11 +++++--
arch/powerpc/include/asm/paca.h | 5 +++
arch/powerpc/kvm/book3s_hv.c | 52 +++++++++++++++++++++++++++++++
arch/powerpc/kvm/trace_hv.h | 27 ++++++++++++++++
4 files changed, 92 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
index 61ec2447dabf..f40a646bee3c 100644
--- a/arch/powerpc/include/asm/lppaca.h
+++ b/arch/powerpc/include/asm/lppaca.h
@@ -62,7 +62,8 @@ struct lppaca {
u8 donate_dedicated_cpu; /* Donate dedicated CPU cycles */
u8 fpregs_in_use;
u8 pmcregs_in_use;
- u8 reserved8[28];
+ u8 l2_counters_enable; /* Enable usage of counters for KVM guest */
+ u8 reserved8[27];
__be64 wait_state_cycles; /* Wait cycles for this proc */
u8 reserved9[28];
__be16 slb_count; /* # of SLBs to maintain */
@@ -92,9 +93,13 @@ struct lppaca {
/* cacheline 4-5 */
__be32 page_ins; /* CMO Hint - # page ins by OS */
- u8 reserved12[148];
+ u8 reserved12[28];
+ volatile __be64 l1_to_l2_cs_tb;
+ volatile __be64 l2_to_l1_cs_tb;
+ volatile __be64 l2_runtime_tb;
+ u8 reserved13[96];
volatile __be64 dtl_idx; /* Dispatch Trace Log head index */
- u8 reserved13[96];
+ u8 reserved14[96];
} ____cacheline_aligned;
#define lppaca_of(cpu) (*paca_ptrs[cpu]->lppaca_ptr)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 1d58da946739..f20ac7a6efa4 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -278,6 +278,11 @@ struct paca_struct {
struct mce_info *mce_info;
u8 mce_pending_irq_work;
#endif /* CONFIG_PPC_BOOK3S_64 */
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+ u64 l1_to_l2_cs;
+ u64 l2_to_l1_cs;
+ u64 l2_runtime_agg;
+#endif
} ____cacheline_aligned;
extern void copy_mm_to_paca(struct mm_struct *mm);
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 8e86eb577eb8..ed69ad58bd02 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
}
}
+static inline int kvmhv_get_l2_counters_status(void)
+{
+ return get_lppaca()->l2_counters_enable;
+}
+
+static inline void kvmhv_set_l2_counters_status(int cpu, bool status)
+{
+ if (status)
+ lppaca_of(cpu).l2_counters_enable = 1;
+ else
+ lppaca_of(cpu).l2_counters_enable = 0;
+}
+
+int kmvhv_counters_tracepoint_regfunc(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ kvmhv_set_l2_counters_status(cpu, true);
+ }
+ return 0;
+}
+
+void kmvhv_counters_tracepoint_unregfunc(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ kvmhv_set_l2_counters_status(cpu, false);
+ }
+}
+
+static void do_trace_nested_cs_time(struct kvm_vcpu *vcpu)
+{
+ struct lppaca *lp = get_lppaca();
+ u64 l1_to_l2_ns, l2_to_l1_ns, l2_runtime_ns;
+
+ l1_to_l2_ns = tb_to_ns(be64_to_cpu(lp->l1_to_l2_cs_tb));
+ l2_to_l1_ns = tb_to_ns(be64_to_cpu(lp->l2_to_l1_cs_tb));
+ l2_runtime_ns = tb_to_ns(be64_to_cpu(lp->l2_runtime_tb));
+ trace_kvmppc_vcpu_stats(vcpu, l1_to_l2_ns - local_paca->l1_to_l2_cs,
+ l2_to_l1_ns - local_paca->l2_to_l1_cs,
+ l2_runtime_ns - local_paca->l2_runtime_agg);
+ local_paca->l1_to_l2_cs = l1_to_l2_ns;
+ local_paca->l2_to_l1_cs = l2_to_l1_ns;
+ local_paca->l2_runtime_agg = l2_runtime_ns;
+}
+
static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
unsigned long lpcr, u64 *tb)
{
@@ -4156,6 +4204,10 @@ static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
timer_rearm_host_dec(*tb);
+ /* Record context switch and guest_run_time data */
+ if (kvmhv_get_l2_counters_status())
+ do_trace_nested_cs_time(vcpu);
+
return trap;
}
diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
index 8d57c8428531..dc118ab88f23 100644
--- a/arch/powerpc/kvm/trace_hv.h
+++ b/arch/powerpc/kvm/trace_hv.h
@@ -238,6 +238,9 @@
{H_MULTI_THREADS_ACTIVE, "H_MULTI_THREADS_ACTIVE"}, \
{H_OUTSTANDING_COP_OPS, "H_OUTSTANDING_COP_OPS"}
+int kmvhv_counters_tracepoint_regfunc(void);
+void kmvhv_counters_tracepoint_unregfunc(void);
+
TRACE_EVENT(kvm_guest_enter,
TP_PROTO(struct kvm_vcpu *vcpu),
TP_ARGS(vcpu),
@@ -512,6 +515,30 @@ TRACE_EVENT(kvmppc_run_vcpu_exit,
__entry->vcpu_id, __entry->exit, __entry->ret)
);
+TRACE_EVENT_FN(kvmppc_vcpu_stats,
+ TP_PROTO(struct kvm_vcpu *vcpu, u64 l1_to_l2_cs, u64 l2_to_l1_cs, u64 l2_runtime),
+
+ TP_ARGS(vcpu, l1_to_l2_cs, l2_to_l1_cs, l2_runtime),
+
+ TP_STRUCT__entry(
+ __field(int, vcpu_id)
+ __field(u64, l1_to_l2_cs)
+ __field(u64, l2_to_l1_cs)
+ __field(u64, l2_runtime)
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_id = vcpu->vcpu_id;
+ __entry->l1_to_l2_cs = l1_to_l2_cs;
+ __entry->l2_to_l1_cs = l2_to_l1_cs;
+ __entry->l2_runtime = l2_runtime;
+ ),
+
+ TP_printk("VCPU %d: l1_to_l2_cs_time=%llu ns l2_to_l1_cs_time=%llu ns l2_runtime=%llu ns",
+ __entry->vcpu_id, __entry->l1_to_l2_cs,
+ __entry->l2_to_l1_cs, __entry->l2_runtime),
+ kmvhv_counters_tracepoint_regfunc, kmvhv_counters_tracepoint_unregfunc
+);
#endif /* _TRACE_KVM_HV_H */
/* This part must be outside protection */
--
2.44.0
On Mon, May 06, 2024 at 08:26:03PM GMT, Gautam Menghani wrote:
> PAPR hypervisor has introduced three new counters in the VPA area of
> LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
> for context switches from host to guest and vice versa, and 1 counter
> for getting the total time spent inside the KVM guest. Add a tracepoint
> that enables reading the counters for use by ftrace/perf. Note that this
> tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
>
> [1] Terminology:
> a. L1 refers to the VM (LPAR) booted on top of PAPR hypervisor
> b. L2 refers to the KVM guest booted on top of L1.
>
> Signed-off-by: Vaibhav Jain <[email protected]>
> Signed-off-by: Gautam Menghani <[email protected]>
> ---
> v5 -> v6:
> 1. Use TRACE_EVENT_FN to enable/disable counters only once.
> 2. Remove the agg. counters from vcpu->arch.
> 3. Use PACA to maintain old counter values instead of zeroing on every
> entry.
> 4. Simplify variable names
>
> v4 -> v5:
> 1. Define helper functions for getting/setting the accumulation counter
> in L2's VPA
>
> v3 -> v4:
> 1. After vcpu_run, check the VPA flag instead of checking for tracepoint
> being enabled for disabling the cs time accumulation.
>
> v2 -> v3:
> 1. Move the counter disabling and zeroing code to a different function.
> 2. Move the get_lppaca() inside the tracepoint_enabled() branch.
> 3. Add the aggregation logic to maintain total context switch time.
>
> v1 -> v2:
> 1. Fix the build error due to invalid struct member reference.
>
> arch/powerpc/include/asm/lppaca.h | 11 +++++--
> arch/powerpc/include/asm/paca.h | 5 +++
> arch/powerpc/kvm/book3s_hv.c | 52 +++++++++++++++++++++++++++++++
> arch/powerpc/kvm/trace_hv.h | 27 ++++++++++++++++
> 4 files changed, 92 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
> index 61ec2447dabf..f40a646bee3c 100644
> --- a/arch/powerpc/include/asm/lppaca.h
> +++ b/arch/powerpc/include/asm/lppaca.h
> @@ -62,7 +62,8 @@ struct lppaca {
> u8 donate_dedicated_cpu; /* Donate dedicated CPU cycles */
> u8 fpregs_in_use;
> u8 pmcregs_in_use;
> - u8 reserved8[28];
> + u8 l2_counters_enable; /* Enable usage of counters for KVM guest */
> + u8 reserved8[27];
> __be64 wait_state_cycles; /* Wait cycles for this proc */
> u8 reserved9[28];
> __be16 slb_count; /* # of SLBs to maintain */
> @@ -92,9 +93,13 @@ struct lppaca {
> /* cacheline 4-5 */
>
> __be32 page_ins; /* CMO Hint - # page ins by OS */
> - u8 reserved12[148];
> + u8 reserved12[28];
> + volatile __be64 l1_to_l2_cs_tb;
> + volatile __be64 l2_to_l1_cs_tb;
> + volatile __be64 l2_runtime_tb;
> + u8 reserved13[96];
> volatile __be64 dtl_idx; /* Dispatch Trace Log head index */
> - u8 reserved13[96];
> + u8 reserved14[96];
> } ____cacheline_aligned;
>
> #define lppaca_of(cpu) (*paca_ptrs[cpu]->lppaca_ptr)
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index 1d58da946739..f20ac7a6efa4 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -278,6 +278,11 @@ struct paca_struct {
> struct mce_info *mce_info;
> u8 mce_pending_irq_work;
> #endif /* CONFIG_PPC_BOOK3S_64 */
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> + u64 l1_to_l2_cs;
> + u64 l2_to_l1_cs;
> + u64 l2_runtime_agg;
> +#endif
> } ____cacheline_aligned;
>
> extern void copy_mm_to_paca(struct mm_struct *mm);
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 8e86eb577eb8..ed69ad58bd02 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
> }
> }
>
> +static inline int kvmhv_get_l2_counters_status(void)
> +{
> + return get_lppaca()->l2_counters_enable;
> +}
> +
> +static inline void kvmhv_set_l2_counters_status(int cpu, bool status)
> +{
> + if (status)
> + lppaca_of(cpu).l2_counters_enable = 1;
> + else
> + lppaca_of(cpu).l2_counters_enable = 0;
> +}
> +
> +int kmvhv_counters_tracepoint_regfunc(void)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + kvmhv_set_l2_counters_status(cpu, true);
> + }
> + return 0;
> +}
> +
> +void kmvhv_counters_tracepoint_unregfunc(void)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + kvmhv_set_l2_counters_status(cpu, false);
> + }
> +}
> +
> +static void do_trace_nested_cs_time(struct kvm_vcpu *vcpu)
> +{
> + struct lppaca *lp = get_lppaca();
> + u64 l1_to_l2_ns, l2_to_l1_ns, l2_runtime_ns;
> +
> + l1_to_l2_ns = tb_to_ns(be64_to_cpu(lp->l1_to_l2_cs_tb));
> + l2_to_l1_ns = tb_to_ns(be64_to_cpu(lp->l2_to_l1_cs_tb));
> + l2_runtime_ns = tb_to_ns(be64_to_cpu(lp->l2_runtime_tb));
> + trace_kvmppc_vcpu_stats(vcpu, l1_to_l2_ns - local_paca->l1_to_l2_cs,
> + l2_to_l1_ns - local_paca->l2_to_l1_cs,
> + l2_runtime_ns - local_paca->l2_runtime_agg);
Depending on how the hypervisor works, if the vcpu was in l2 when the
tracepoint is enabled, the counters may not be updated on exit and we
may emit a trace with all values zero. If that is possible, it might be
a good idea to only emit the trace if any of the counters are non-zero.
Otherwise, this looks good to me.
Acked-by: Naveen N Rao <[email protected]>
- Naveen
> + local_paca->l1_to_l2_cs = l1_to_l2_ns;
> + local_paca->l2_to_l1_cs = l2_to_l1_ns;
> + local_paca->l2_runtime_agg = l2_runtime_ns;
> +}
> +
> static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
> unsigned long lpcr, u64 *tb)
> {
> @@ -4156,6 +4204,10 @@ static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
>
> timer_rearm_host_dec(*tb);
>
> + /* Record context switch and guest_run_time data */
> + if (kvmhv_get_l2_counters_status())
> + do_trace_nested_cs_time(vcpu);
> +
> return trap;
> }
>
> diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
> index 8d57c8428531..dc118ab88f23 100644
> --- a/arch/powerpc/kvm/trace_hv.h
> +++ b/arch/powerpc/kvm/trace_hv.h
> @@ -238,6 +238,9 @@
> {H_MULTI_THREADS_ACTIVE, "H_MULTI_THREADS_ACTIVE"}, \
> {H_OUTSTANDING_COP_OPS, "H_OUTSTANDING_COP_OPS"}
>
> +int kmvhv_counters_tracepoint_regfunc(void);
> +void kmvhv_counters_tracepoint_unregfunc(void);
> +
> TRACE_EVENT(kvm_guest_enter,
> TP_PROTO(struct kvm_vcpu *vcpu),
> TP_ARGS(vcpu),
> @@ -512,6 +515,30 @@ TRACE_EVENT(kvmppc_run_vcpu_exit,
> __entry->vcpu_id, __entry->exit, __entry->ret)
> );
>
> +TRACE_EVENT_FN(kvmppc_vcpu_stats,
> + TP_PROTO(struct kvm_vcpu *vcpu, u64 l1_to_l2_cs, u64 l2_to_l1_cs, u64 l2_runtime),
> +
> + TP_ARGS(vcpu, l1_to_l2_cs, l2_to_l1_cs, l2_runtime),
> +
> + TP_STRUCT__entry(
> + __field(int, vcpu_id)
> + __field(u64, l1_to_l2_cs)
> + __field(u64, l2_to_l1_cs)
> + __field(u64, l2_runtime)
> + ),
> +
> + TP_fast_assign(
> + __entry->vcpu_id = vcpu->vcpu_id;
> + __entry->l1_to_l2_cs = l1_to_l2_cs;
> + __entry->l2_to_l1_cs = l2_to_l1_cs;
> + __entry->l2_runtime = l2_runtime;
> + ),
> +
> + TP_printk("VCPU %d: l1_to_l2_cs_time=%llu ns l2_to_l1_cs_time=%llu ns l2_runtime=%llu ns",
> + __entry->vcpu_id, __entry->l1_to_l2_cs,
> + __entry->l2_to_l1_cs, __entry->l2_runtime),
> + kmvhv_counters_tracepoint_regfunc, kmvhv_counters_tracepoint_unregfunc
> +);
> #endif /* _TRACE_KVM_HV_H */
>
> /* This part must be outside protection */
> --
> 2.44.0
>
On Tue May 7, 2024 at 12:56 AM AEST, Gautam Menghani wrote:
> PAPR hypervisor has introduced three new counters in the VPA area of
> LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
> for context switches from host to guest and vice versa, and 1 counter
> for getting the total time spent inside the KVM guest. Add a tracepoint
> that enables reading the counters for use by ftrace/perf. Note that this
> tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
>
> [1] Terminology:
> a. L1 refers to the VM (LPAR) booted on top of PAPR hypervisor
> b. L2 refers to the KVM guest booted on top of L1.
>
> Signed-off-by: Vaibhav Jain <[email protected]>
> Signed-off-by: Gautam Menghani <[email protected]>
> ---
> v5 -> v6:
> 1. Use TRACE_EVENT_FN to enable/disable counters only once.
> 2. Remove the agg. counters from vcpu->arch.
> 3. Use PACA to maintain old counter values instead of zeroing on every
> entry.
> 4. Simplify variable names
>
> v4 -> v5:
> 1. Define helper functions for getting/setting the accumulation counter
> in L2's VPA
>
> v3 -> v4:
> 1. After vcpu_run, check the VPA flag instead of checking for tracepoint
> being enabled for disabling the cs time accumulation.
>
> v2 -> v3:
> 1. Move the counter disabling and zeroing code to a different function.
> 2. Move the get_lppaca() inside the tracepoint_enabled() branch.
> 3. Add the aggregation logic to maintain total context switch time.
>
> v1 -> v2:
> 1. Fix the build error due to invalid struct member reference.
>
> arch/powerpc/include/asm/lppaca.h | 11 +++++--
> arch/powerpc/include/asm/paca.h | 5 +++
> arch/powerpc/kvm/book3s_hv.c | 52 +++++++++++++++++++++++++++++++
> arch/powerpc/kvm/trace_hv.h | 27 ++++++++++++++++
> 4 files changed, 92 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
> index 61ec2447dabf..f40a646bee3c 100644
> --- a/arch/powerpc/include/asm/lppaca.h
> +++ b/arch/powerpc/include/asm/lppaca.h
> @@ -62,7 +62,8 @@ struct lppaca {
> u8 donate_dedicated_cpu; /* Donate dedicated CPU cycles */
> u8 fpregs_in_use;
> u8 pmcregs_in_use;
> - u8 reserved8[28];
> + u8 l2_counters_enable; /* Enable usage of counters for KVM guest */
> + u8 reserved8[27];
> __be64 wait_state_cycles; /* Wait cycles for this proc */
> u8 reserved9[28];
> __be16 slb_count; /* # of SLBs to maintain */
> @@ -92,9 +93,13 @@ struct lppaca {
> /* cacheline 4-5 */
>
> __be32 page_ins; /* CMO Hint - # page ins by OS */
> - u8 reserved12[148];
> + u8 reserved12[28];
> + volatile __be64 l1_to_l2_cs_tb;
> + volatile __be64 l2_to_l1_cs_tb;
> + volatile __be64 l2_runtime_tb;
I wonder if we shouldn't be moving over to use READ_ONCE for these
instead of volatile.
Probably doesn't really matter here. Maybe general audit of volatiles
in arch/powerpc could be something to put in linuxppc issues.
> + u8 reserved13[96];
> volatile __be64 dtl_idx; /* Dispatch Trace Log head index */
> - u8 reserved13[96];
> + u8 reserved14[96];
> } ____cacheline_aligned;
>
> #define lppaca_of(cpu) (*paca_ptrs[cpu]->lppaca_ptr)
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index 1d58da946739..f20ac7a6efa4 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -278,6 +278,11 @@ struct paca_struct {
> struct mce_info *mce_info;
> u8 mce_pending_irq_work;
> #endif /* CONFIG_PPC_BOOK3S_64 */
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> + u64 l1_to_l2_cs;
> + u64 l2_to_l1_cs;
> + u64 l2_runtime_agg;
> +#endif
> } ____cacheline_aligned;
I don't think these really need to be in the paca.
paca is for per-cpu stuff that is accessed in real mode, early interrupt
entry, etc.
>
> extern void copy_mm_to_paca(struct mm_struct *mm);
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 8e86eb577eb8..ed69ad58bd02 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
> }
> }
>
> +static inline int kvmhv_get_l2_counters_status(void)
> +{
> + return get_lppaca()->l2_counters_enable;
> +}
> +
> +static inline void kvmhv_set_l2_counters_status(int cpu, bool status)
> +{
> + if (status)
> + lppaca_of(cpu).l2_counters_enable = 1;
> + else
> + lppaca_of(cpu).l2_counters_enable = 0;
> +}
> +
> +int kmvhv_counters_tracepoint_regfunc(void)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + kvmhv_set_l2_counters_status(cpu, true);
> + }
> + return 0;
> +}
> +
> +void kmvhv_counters_tracepoint_unregfunc(void)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + kvmhv_set_l2_counters_status(cpu, false);
> + }
> +}
> +
> +static void do_trace_nested_cs_time(struct kvm_vcpu *vcpu)
> +{
> + struct lppaca *lp = get_lppaca();
> + u64 l1_to_l2_ns, l2_to_l1_ns, l2_runtime_ns;
> +
> + l1_to_l2_ns = tb_to_ns(be64_to_cpu(lp->l1_to_l2_cs_tb));
> + l2_to_l1_ns = tb_to_ns(be64_to_cpu(lp->l2_to_l1_cs_tb));
> + l2_runtime_ns = tb_to_ns(be64_to_cpu(lp->l2_runtime_tb));
> + trace_kvmppc_vcpu_stats(vcpu, l1_to_l2_ns - local_paca->l1_to_l2_cs,
> + l2_to_l1_ns - local_paca->l2_to_l1_cs,
> + l2_runtime_ns - local_paca->l2_runtime_agg);
> + local_paca->l1_to_l2_cs = l1_to_l2_ns;
> + local_paca->l2_to_l1_cs = l2_to_l1_ns;
> + local_paca->l2_runtime_agg = l2_runtime_ns;
> +}
So you're just using the per-cpu values to cache the last value
read so next time you can take a delta.
Could you zero the counters before entry? Or just use local
variables to read the before values.
If you want to keep the same scheme, I think per-cpu variables
should work.
Otherwise,
Reviewed-by: Nicholas Piggin <[email protected]>
> +
> static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
> unsigned long lpcr, u64 *tb)
> {
> @@ -4156,6 +4204,10 @@ static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
>
> timer_rearm_host_dec(*tb);
>
> + /* Record context switch and guest_run_time data */
> + if (kvmhv_get_l2_counters_status())
> + do_trace_nested_cs_time(vcpu);
> +
> return trap;
> }
>
> diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
> index 8d57c8428531..dc118ab88f23 100644
> --- a/arch/powerpc/kvm/trace_hv.h
> +++ b/arch/powerpc/kvm/trace_hv.h
> @@ -238,6 +238,9 @@
> {H_MULTI_THREADS_ACTIVE, "H_MULTI_THREADS_ACTIVE"}, \
> {H_OUTSTANDING_COP_OPS, "H_OUTSTANDING_COP_OPS"}
>
> +int kmvhv_counters_tracepoint_regfunc(void);
> +void kmvhv_counters_tracepoint_unregfunc(void);
> +
> TRACE_EVENT(kvm_guest_enter,
> TP_PROTO(struct kvm_vcpu *vcpu),
> TP_ARGS(vcpu),
> @@ -512,6 +515,30 @@ TRACE_EVENT(kvmppc_run_vcpu_exit,
> __entry->vcpu_id, __entry->exit, __entry->ret)
> );
>
> +TRACE_EVENT_FN(kvmppc_vcpu_stats,
> + TP_PROTO(struct kvm_vcpu *vcpu, u64 l1_to_l2_cs, u64 l2_to_l1_cs, u64 l2_runtime),
> +
> + TP_ARGS(vcpu, l1_to_l2_cs, l2_to_l1_cs, l2_runtime),
> +
> + TP_STRUCT__entry(
> + __field(int, vcpu_id)
> + __field(u64, l1_to_l2_cs)
> + __field(u64, l2_to_l1_cs)
> + __field(u64, l2_runtime)
> + ),
> +
> + TP_fast_assign(
> + __entry->vcpu_id = vcpu->vcpu_id;
> + __entry->l1_to_l2_cs = l1_to_l2_cs;
> + __entry->l2_to_l1_cs = l2_to_l1_cs;
> + __entry->l2_runtime = l2_runtime;
> + ),
> +
> + TP_printk("VCPU %d: l1_to_l2_cs_time=%llu ns l2_to_l1_cs_time=%llu ns l2_runtime=%llu ns",
> + __entry->vcpu_id, __entry->l1_to_l2_cs,
> + __entry->l2_to_l1_cs, __entry->l2_runtime),
> + kmvhv_counters_tracepoint_regfunc, kmvhv_counters_tracepoint_unregfunc
> +);
> #endif /* _TRACE_KVM_HV_H */
>
> /* This part must be outside protection */
Gautam Menghani <[email protected]> writes:
> PAPR hypervisor has introduced three new counters in the VPA area of
> LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
> for context switches from host to guest and vice versa, and 1 counter
> for getting the total time spent inside the KVM guest. Add a tracepoint
> that enables reading the counters for use by ftrace/perf. Note that this
> tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
..
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 8e86eb577eb8..ed69ad58bd02 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
> }
> }
>
> +static inline int kvmhv_get_l2_counters_status(void)
> +{
> + return get_lppaca()->l2_counters_enable;
> +}
This is breaking the powernv build:
$ make powernv_defconfig ; make -s -j (nproc)
make[1]: Entering directory '/home/michael/linux/.build'
GEN Makefile
#
# configuration written to .config
#
make[1]: Leaving directory '/home/michael/linux/.build'
./arch/powerpc/kvm/book3s_hv.c: In function ‘kvmhv_get_l2_counters_status’:
./arch/powerpc/kvm/book3s_hv.c:4113:16: error: implicit declaration of function ‘get_lppaca’; did you mean ‘get_paca’? [-Werror=implicit-function-declaration]
4113 | return get_lppaca()->l2_counters_enable;
| ^~~~~~~~~~
| get_paca
./arch/powerpc/kvm/book3s_hv.c:4113:28: error: invalid type argument of ‘->’ (have ‘int’)
4113 | return get_lppaca()->l2_counters_enable;
| ^~
In file included from ../arch/powerpc/include/asm/paravirt.h:9,
from ../arch/powerpc/include/asm/qspinlock.h:7,
from ../arch/powerpc/include/asm/spinlock.h:7,
from ../include/linux/spinlock.h:95,
from ../include/linux/sched.h:2138,
from ../include/linux/hardirq.h:9,
from ../include/linux/kvm_host.h:7,
from ../arch/powerpc/kvm/book3s_hv.c:18:
./arch/powerpc/kvm/book3s_hv.c: In function ‘kvmhv_set_l2_counters_status’:
./arch/powerpc/include/asm/lppaca.h:105:41: error: ‘struct paca_struct’ has no member named ‘lppaca_ptr’
105 | #define lppaca_of(cpu) (*paca_ptrs[cpu]->lppaca_ptr)
| ^~
./arch/powerpc/kvm/book3s_hv.c:4119:17: note: in expansion of macro ‘lppaca_of’
4119 | lppaca_of(cpu).l2_counters_enable = 1;
| ^~~~~~~~~
./arch/powerpc/include/asm/lppaca.h:105:41: error: ‘struct paca_struct’ has no member named ‘lppaca_ptr’
105 | #define lppaca_of(cpu) (*paca_ptrs[cpu]->lppaca_ptr)
| ^~
./arch/powerpc/kvm/book3s_hv.c:4121:17: note: in expansion of macro ‘lppaca_of’
4121 | lppaca_of(cpu).l2_counters_enable = 0;
| ^~~~~~~~~
./arch/powerpc/kvm/book3s_hv.c: In function ‘do_trace_nested_cs_time’:
./arch/powerpc/kvm/book3s_hv.c:4145:29: error: initialization of ‘struct lppaca *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
4145 | struct lppaca *lp = get_lppaca();
| ^~~~~~~~~~
./arch/powerpc/kvm/book3s_hv.c: In function ‘kvmhv_get_l2_counters_status’:
./arch/powerpc/kvm/book3s_hv.c:4114:1: error: control reaches end of non-void function [-Werror=return-type]
4114 | }
| ^
cc1: all warnings being treated as errors
make[5]: *** [../scripts/Makefile.build:244: arch/powerpc/kvm/book3s_hv.o] Error 1
make[5]: *** Waiting for unfinished jobs....
make[4]: *** [../scripts/Makefile.build:485: arch/powerpc/kvm] Error 2
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [../scripts/Makefile.build:485: arch/powerpc] Error 2
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [/home/michael/linux/Makefile:1919: .] Error 2
make[1]: *** [/home/michael/linux/Makefile:240: __sub-make] Error 2
make: *** [Makefile:240: __sub-make] Error 2
cheers
On Wed May 8, 2024 at 10:36 PM AEST, Michael Ellerman wrote:
> Gautam Menghani <[email protected]> writes:
> > PAPR hypervisor has introduced three new counters in the VPA area of
> > LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
> > for context switches from host to guest and vice versa, and 1 counter
> > for getting the total time spent inside the KVM guest. Add a tracepoint
> > that enables reading the counters for use by ftrace/perf. Note that this
> > tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
> ...
> > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> > index 8e86eb577eb8..ed69ad58bd02 100644
> > --- a/arch/powerpc/kvm/book3s_hv.c
> > +++ b/arch/powerpc/kvm/book3s_hv.c
> > @@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
> > }
> > }
> >
> > +static inline int kvmhv_get_l2_counters_status(void)
> > +{
> > + return get_lppaca()->l2_counters_enable;
> > +}
>
> This is breaking the powernv build:
[...]
All the nested KVM code should really go under CONFIG_PSERIES.
Possibly even moved out to its own file.
For now maybe you could just ifdef these few functions and
replace with noop variants for !PSERIES.
Thanks,
Nick