Commit e1f288d2 authored by Gautam Menghani's avatar Gautam Menghani Committed by Michael Ellerman
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KVM: PPC: Book3S HV nestedv2: Add support for reading VPA counters for pseries guests 



PAPR hypervisor has introduced three new counters in the VPA area of
LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - two
for context switches from host to guest and vice versa, and one 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.

Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Acked-by: default avatarNaveen N Rao <naveen@kernel.org>
Signed-off-by: default avatarVaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: default avatarGautam Menghani <gautam@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240520175742.196329-1-gautam@linux.ibm.com
parent c3f38fa6

arch/powerpc/include/asm/kvm_book3s_64.h

+5 −0
Original line number Diff line number Diff line
@@ -684,6 +684,11 @@ int kvmhv_nestedv2_set_ptbl_entry(unsigned long lpid, u64 dw0, u64 dw1); 
int kvmhv_nestedv2_parse_output(struct kvm_vcpu *vcpu);

int kvmhv_nestedv2_set_vpa(struct kvm_vcpu *vcpu, unsigned long vpa);



int kmvhv_counters_tracepoint_regfunc(void);

void kmvhv_counters_tracepoint_unregfunc(void);

int kvmhv_get_l2_counters_status(void);

void kvmhv_set_l2_counters_status(int cpu, bool status);



#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */



#endif /* __ASM_KVM_BOOK3S_64_H__ */

arch/powerpc/include/asm/lppaca.h

+8 −3
Original line number Diff line number Diff line
@@ -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];

	volatile __be64 dtl_idx;	/* Dispatch Trace Log head index */

	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	reserved14[96];

} ____cacheline_aligned;



#define lppaca_of(cpu)	(*paca_ptrs[cpu]->lppaca_ptr)

arch/powerpc/kvm/book3s_hv.c

+75 −0
Original line number Diff line number Diff line
@@ -4108,6 +4108,77 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu) 
	}

}



/* Helper functions for reading L2's stats from L1's VPA */

#ifdef CONFIG_PPC_PSERIES

static DEFINE_PER_CPU(u64, l1_to_l2_cs);

static DEFINE_PER_CPU(u64, l2_to_l1_cs);

static DEFINE_PER_CPU(u64, l2_runtime_agg);



int kvmhv_get_l2_counters_status(void)

{

	return firmware_has_feature(FW_FEATURE_LPAR) &&

		get_lppaca()->l2_counters_enable;

}



void kvmhv_set_l2_counters_status(int cpu, bool status)

{

	if (!firmware_has_feature(FW_FEATURE_LPAR))

		return;

	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_present_cpu(cpu) {

		kvmhv_set_l2_counters_status(cpu, true);

	}

	return 0;

}



void kmvhv_counters_tracepoint_unregfunc(void)

{

	int cpu;



	for_each_present_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;

	u64 *l1_to_l2_cs_ptr = this_cpu_ptr(&l1_to_l2_cs);

	u64 *l2_to_l1_cs_ptr = this_cpu_ptr(&l2_to_l1_cs);

	u64 *l2_runtime_agg_ptr = this_cpu_ptr(&l2_runtime_agg);



	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 - *l1_to_l2_cs_ptr,

					l2_to_l1_ns - *l2_to_l1_cs_ptr,

					l2_runtime_ns - *l2_runtime_agg_ptr);

	*l1_to_l2_cs_ptr = l1_to_l2_ns;

	*l2_to_l1_cs_ptr = l2_to_l1_ns;

	*l2_runtime_agg_ptr = l2_runtime_ns;

}



#else

int kvmhv_get_l2_counters_status(void)

{

	return 0;

}



static void do_trace_nested_cs_time(struct kvm_vcpu *vcpu)

{

}

#endif



static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,

				     unsigned long lpcr, u64 *tb)

{
@@ -4156,6 +4227,10 @@ 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;

}

arch/powerpc/kvm/trace_hv.h

+29 −0
Original line number Diff line number Diff line
@@ -512,6 +512,35 @@ TRACE_EVENT(kvmppc_run_vcpu_exit, 
			__entry->vcpu_id, __entry->exit, __entry->ret)

);



#ifdef CONFIG_PPC_PSERIES



TRACE_EVENT_FN_COND(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_CONDITION(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

#endif /* _TRACE_KVM_HV_H */



/* This part must be outside protection */