linux-kernel - Re: [PATCH v2 2/2] riscv: KVM: add basic support for host vs guest profiling

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Message-ID: <3e5e4ba4-acb6-4cea-96f8-b16886bb6285@iscas.ac.cn>
Date: Thu, 22 Aug 2024 14:42:53 +0800
From: Quan Zhou <zhouquan@...as.ac.cn>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: anup@...infault.org, atishp@...shpatra.org, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
 kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
 linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: KVM: add basic support for host vs guest
 profiling


On 2024/8/21 20:51, Andrew Jones wrote:
> On Tue, Aug 13, 2024 at 09:24:10PM GMT, zhouquan@...as.ac.cn wrote:
>> From: Quan Zhou <zhouquan@...as.ac.cn>
>>
>> For the information collected on the host side, we need to
>> identify which data originates from the guest and record
>> these events separately, this can be achieved by having
>> KVM register perf callbacks.
>>
>> Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
>> ---
>>   arch/riscv/include/asm/kvm_host.h |  5 +++++
>>   arch/riscv/kvm/Kconfig            |  1 +
>>   arch/riscv/kvm/main.c             | 12 ++++++++++--
>>   arch/riscv/kvm/vcpu.c             |  7 +++++++
>>   4 files changed, 23 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
>> index 2e2254fd2a2a..d2350b08a3f4 100644
>> --- a/arch/riscv/include/asm/kvm_host.h
>> +++ b/arch/riscv/include/asm/kvm_host.h
>> @@ -286,6 +286,11 @@ struct kvm_vcpu_arch {
>>   	} sta;
>>   };
>>
> 
> Let's add the same comment here that arm64 has unless you determine
> that 'any event that arrives while a vCPU is loaded is considered to be
> "in guest"' is not true for riscv.
> 

Ok, i will add this comment to clarify the point.

Thanks,
Quan

>> +static inline bool kvm_arch_pmi_in_guest(struct kvm_vcpu *vcpu)
>> +{
>> +	return IS_ENABLED(CONFIG_GUEST_PERF_EVENTS) && !!vcpu;
>> +}
>> +
>>   static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>>   
>>   #define KVM_RISCV_GSTAGE_TLB_MIN_ORDER		12
>> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
>> index 26d1727f0550..0c3cbb0915ff 100644
>> --- a/arch/riscv/kvm/Kconfig
>> +++ b/arch/riscv/kvm/Kconfig
>> @@ -32,6 +32,7 @@ config KVM
>>   	select KVM_XFER_TO_GUEST_WORK
>>   	select KVM_GENERIC_MMU_NOTIFIER
>>   	select SCHED_INFO
>> +	select GUEST_PERF_EVENTS if PERF_EVENTS
>>   	help
>>   	  Support hosting virtualized guest machines.
>>   
>> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
>> index bab2ec34cd87..734b48d8f6dd 100644
>> --- a/arch/riscv/kvm/main.c
>> +++ b/arch/riscv/kvm/main.c
>> @@ -51,6 +51,12 @@ void kvm_arch_hardware_disable(void)
>>   	csr_write(CSR_HIDELEG, 0);
>>   }
>>   
>> +static void kvm_riscv_teardown(void)
>> +{
>> +	kvm_riscv_aia_exit();
>> +	kvm_unregister_perf_callbacks();
>> +}
>> +
>>   static int __init riscv_kvm_init(void)
>>   {
>>   	int rc;
>> @@ -105,9 +111,11 @@ static int __init riscv_kvm_init(void)
>>   		kvm_info("AIA available with %d guest external interrupts\n",
>>   			 kvm_riscv_aia_nr_hgei);
>>   
>> +	kvm_register_perf_callbacks(NULL);
>> +
>>   	rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
>>   	if (rc) {
>> -		kvm_riscv_aia_exit();
>> +		kvm_riscv_teardown();
>>   		return rc;
>>   	}
>>   
>> @@ -117,7 +125,7 @@ module_init(riscv_kvm_init);
>>   
>>   static void __exit riscv_kvm_exit(void)
>>   {
>> -	kvm_riscv_aia_exit();
>> +	kvm_riscv_teardown();
>>   
>>   	kvm_exit();
>>   }
>> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
>> index 8d7d381737ee..e8ffb3456898 100644
>> --- a/arch/riscv/kvm/vcpu.c
>> +++ b/arch/riscv/kvm/vcpu.c
>> @@ -226,6 +226,13 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
>>   	return (vcpu->arch.guest_context.sstatus & SR_SPP) ? true : false;
>>   }
>>   
>> +#ifdef CONFIG_GUEST_PERF_EVENTS
>> +unsigned long kvm_arch_vcpu_get_ip(struct kvm_vcpu *vcpu)
>> +{
>> +	return vcpu->arch.guest_context.sepc;
>> +}
>> +#endif
>> +
>>   vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
>>   {
>>   	return VM_FAULT_SIGBUS;
>> -- 
>> 2.34.1
>>
> 
> Thanks,
> drew