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

Andrew Jones
2024-08-21T12:51:12Z

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.

> +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