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Tue, 26 Mar 2024 09:40:37 +0000 (GMT) From: Gautam Menghani To: mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, aneesh.kumar@kernel.org, naveen.n.rao@linux.ibm.com Cc: Gautam Menghani , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Vaibhav Jain Subject: [PATCH v4] arch/powerpc/kvm: Add support for reading VPA counters for pseries guests Date: Tue, 26 Mar 2024 15:10:34 +0530 Message-ID: <20240326094035.115835-1-gautam@linux.ibm.com> X-Mailer: git-send-email 2.44.0 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: BAQ576wi2XwAlqW_H3TqgG1yWY80G5Bp X-Proofpoint-ORIG-GUID: yCeQNG7Mp8v8A4QvUMBUqeyNm0qA3gRq X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-03-26_04,2024-03-21_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 phishscore=0 impostorscore=0 malwarescore=0 mlxscore=0 adultscore=0 clxscore=1015 bulkscore=0 suspectscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2403210000 definitions=main-2403260065 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). Also maintain an aggregation of the context switch times in vcpu->arch. This will be useful in getting the aggregate times with a pmu driver which will be upstreamed in the near future. [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 Signed-off-by: Gautam Menghani --- v1 -> v2: 1. Fix the build error due to invalid struct member reference. 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. v3 -> v4: 1. After vcpu_run, check the VPA flag instead of checking for tracepoint being enabled for disabling the cs time accumulation. arch/powerpc/include/asm/kvm_host.h | 5 +++++ arch/powerpc/include/asm/lppaca.h | 11 ++++++++--- arch/powerpc/kvm/book3s_hv.c | 30 +++++++++++++++++++++++++++++ arch/powerpc/kvm/trace_hv.h | 25 ++++++++++++++++++++++++ 4 files changed, 68 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 8abac5321..d953b32dd 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; + + /* Aggregate context switch and guest run time info (in ns) */ + u64 l1_to_l2_cs_agg; + u64 l2_to_l1_cs_agg; + u64 l2_runtime_agg; #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 8e86eb577..dcd6edd3b 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4108,6 +4108,27 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu) } } +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_exit_cs_time(vcpu, l1_to_l2_ns, l2_to_l1_ns, + l2_runtime_ns); + lp->l1_to_l2_cs_tb = 0; + lp->l2_to_l1_cs_tb = 0; + lp->l2_runtime_tb = 0; + lp->l2_accumul_cntrs_enable = 0; + + // Maintain an aggregate of context switch times + vcpu->arch.l1_to_l2_cs_agg += l1_to_l2_ns; + vcpu->arch.l2_to_l1_cs_agg += l2_to_l1_ns; + vcpu->arch.l2_runtime_agg += l2_runtime_ns; +} + static int kvmhv_vcpu_entry_nestedv2(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr, u64 *tb) { @@ -4130,6 +4151,11 @@ 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); + + /* Enable the guest host context switch time tracking */ + if (unlikely(trace_kvmppc_vcpu_exit_cs_time_enabled())) + get_lppaca()->l2_accumul_cntrs_enable = 1; + rc = plpar_guest_run_vcpu(0, vcpu->kvm->arch.lpid, vcpu->vcpu_id, &trap, &i); @@ -4156,6 +4182,10 @@ 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 (get_lppaca()->l2_accumul_cntrs_enable) + 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 8d57c8428..ab19977c9 100644 --- a/arch/powerpc/kvm/trace_hv.h +++ b/arch/powerpc/kvm/trace_hv.h @@ -491,6 +491,31 @@ 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, 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_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 = l1_to_l2_cs; + __entry->l2_to_l1_cs_ns = l2_to_l1_cs; + __entry->l2_runtime_ns = 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),