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Wed, 27 Mar 2024 13:07:13 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E410C20043; Wed, 27 Mar 2024 13:07:10 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3502720040; Wed, 27 Mar 2024 13:07:07 +0000 (GMT) Received: from [9.171.20.231] (unknown [9.171.20.231]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 27 Mar 2024 13:07:06 +0000 (GMT) Content-Type: multipart/alternative; boundary="------------h9nzZo2uv0YmqUz3TuIoz8BA" Message-ID: <3fde44fe-c51a-43ed-847d-d30948504097@linux.ibm.com> Date: Wed, 27 Mar 2024 18:37:04 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] arch/powerpc/kvm: Add support for reading VPA counters for pseries guests To: Gautam Menghani , mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, aneesh.kumar@kernel.org, naveen.n.rao@linux.ibm.com References: <20240326094035.115835-1-gautam@linux.ibm.com> Content-Language: en-US From: Madhavan Srinivasan In-Reply-To: <20240326094035.115835-1-gautam@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 591AeM7fiW0ZiQtYno-WAOXW3G72ttX3 X-Proofpoint-GUID: YQiLV80SXsJRJIGe869_ryDYiInxRjol 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=2024-03-27_08,2024-03-27_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 bulkscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 phishscore=0 suspectscore=0 spamscore=0 priorityscore=1501 mlxscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2403210000 definitions=main-2403270089 X-Mailman-Approved-At: Thu, 28 Mar 2024 08:10:21 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vaibhav Jain , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This is a multi-part message in MIME format. --------------h9nzZo2uv0YmqUz3TuIoz8BA Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/26/24 3:10 PM, 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). > > 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; can we wrap "get_lppaca()->l2_accumul_cntrs_enable" under wrapper function like is_l2_accumul_cntrs_enable(), set_l2_accumul_cntrs_enable() and unset_l2_accumul_cntrs_enable()? set/unset does not need a parameter and in future incase if we want to check and set or check and unset, we could have additional code in there. Maddy > + > 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), > --------------h9nzZo2uv0YmqUz3TuIoz8BA Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit


On 3/26/24 3:10 PM, 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).

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 <vaibhav@linux.ibm.com>
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
---
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;

can we wrap "get_lppaca()->l2_accumul_cntrs_enable" under wrapper function
like is_l2_accumul_cntrs_enable(), set_l2_accumul_cntrs_enable() and
unset_l2_accumul_cntrs_enable()?

set/unset does not need a parameter and in future incase if we want to
check and set or check and unset, we could have additional code in there.

Maddy

+
 	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),
--------------h9nzZo2uv0YmqUz3TuIoz8BA--