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Message-ID: <20240319142807.95547-1-gautam@linux.ibm.com>
Date: Tue, 19 Mar 2024 19:58:04 +0530
From: Gautam Menghani <gautam@...ux.ibm.com>
To: mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
aneesh.kumar@...nel.org, naveen.n.rao@...ux.ibm.com
Cc: Gautam Menghani <gautam@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
Vaibhav Jain <vaibhav@...ux.ibm.com>
Subject: [PATCH] arch/powerpc/kvm: 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 - 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 <vaibhav@...ux.ibm.com>
Signed-off-by: Gautam Menghani <gautam@...ux.ibm.com>
---
arch/powerpc/include/asm/kvm_host.h | 5 +++++
arch/powerpc/include/asm/lppaca.h | 11 ++++++++---
arch/powerpc/kvm/book3s_hv.c | 20 ++++++++++++++++++++
arch/powerpc/kvm/trace_hv.h | 24 ++++++++++++++++++++++++
4 files changed, 57 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 8abac5321..26d7bb4b9 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -847,6 +847,11 @@ struct kvm_vcpu_arch {
gpa_t nested_io_gpr;
/* For nested APIv2 guests*/
struct kvmhv_nestedv2_io nestedv2_io;
+
+ /* For VPA counters having context switch and guest run time info (in ns) */
+ u64 l1_to_l2_cs;
+ u64 l2_to_l1_cs;
+ u64 l2_runtime;
#endif
#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
index 61ec2447d..bda6b86b9 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_accumul_cntrs_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/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 2b04eba90..b94461b5f 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4092,6 +4092,7 @@ static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
unsigned long msr, i;
int trap;
long rc;
+ struct lppaca *lp = get_lppaca();
io = &vcpu->arch.nestedv2_io;
@@ -4107,6 +4108,17 @@ static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit,
kvmppc_gse_put_u64(io->vcpu_run_input, KVMPPC_GSID_LPCR, lpcr);
accumulate_time(vcpu, &vcpu->arch.in_guest);
+
+ /* Reset the guest host context switch timing */
+ if (unlikely(trace_kvmppc_vcpu_exit_cs_time_enabled())) {
+ lp->l2_accumul_cntrs_enable = 1;
+ lp->l1_to_l2_cs_tb = 0;
+ lp->l2_to_l1_cs_tb = 0;
+ lp->l2_runtime_tb = 0;
+ } else {
+ lp->l2_accumul_cntrs_enable = 0;
+ }
+
rc = plpar_guest_run_vcpu(0, vcpu->kvm->arch.lpid, vcpu->vcpu_id,
&trap, &i);
@@ -4133,6 +4145,14 @@ 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 (unlikely(trace_kvmppc_vcpu_exit_cs_time_enabled())) {
+ vcpu->arch.l1_to_l2_cs = tb_to_ns(be64_to_cpu(lp->l1_to_l2_cs_tb));
+ vcpu->arch.l2_to_l1_cs = tb_to_ns(be64_to_cpu(lp->l2_to_l1_cs_tb));
+ vcpu->arch.l2_runtime = tb_to_ns(be64_to_cpu(lp->l2_runtime_tb));
+ trace_kvmppc_vcpu_exit_cs_time(vcpu);
+ }
+
return trap;
}
diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
index 8d57c8428..10b8f6e5a 100644
--- a/arch/powerpc/kvm/trace_hv.h
+++ b/arch/powerpc/kvm/trace_hv.h
@@ -491,6 +491,30 @@ TRACE_EVENT(kvmppc_run_vcpu_enter,
TP_printk("VCPU %d: tgid=%d", __entry->vcpu_id, __entry->tgid)
);
+TRACE_EVENT(kvmppc_vcpu_exit_cs_time,
+ TP_PROTO(struct kvm_vcpu *vcpu),
+
+ TP_ARGS(vcpu),
+
+ TP_STRUCT__entry(
+ __field(int, vcpu_id)
+ __field(__u64, l1_to_l2_cs_ns)
+ __field(__u64, l2_to_l1_cs_ns)
+ __field(__u64, l2_runtime_ns)
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_id = vcpu->vcpu_id;
+ __entry->l1_to_l2_cs_ns = vcpu->arch.l1_to_l2_cs;
+ __entry->l2_to_l1_cs_ns = vcpu->arch.l2_to_l1_cs;
+ __entry->l2_runtime_ns = vcpu->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_ns,
+ __entry->l2_to_l1_cs_ns, __entry->l2_runtime_ns)
+);
+
TRACE_EVENT(kvmppc_run_vcpu_exit,
TP_PROTO(struct kvm_vcpu *vcpu),
--
2.43.2
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