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

Quan Zhou
2024-08-22T06:43:07Z

On 2024/8/21 20:51, Andrew Jones wrote:
> On Tue, Aug 13, 2024 at 09:24:10PM GMT, zhouquan@iscas.ac.cn wrote:
>> From: Quan Zhou <zhouquan@iscas.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@iscas.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