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

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Message-ID: <20240821-5284bf727abbb08a379e1d06@orel>
Date: Wed, 21 Aug 2024 14:51:09 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: zhouquan@...as.ac.cn
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 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.

> +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