linux-kernel - Re: [PATCH v2 1/2] KVM: x86: Print names of apicv inhibit reasons in traces

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Date: Wed, 8 May 2024 16:50:49 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>, kvm@...r.kernel.org,
 seanjc@...gle.com
Cc: pbonzini@...hat.com, linux-kernel@...r.kernel.org,
 joao.m.martins@...cle.com, boris.ostrovsky@...cle.com,
 suravee.suthikulpanit@....com, mlevitsk@...hat.com
Subject: Re: [PATCH v2 1/2] KVM: x86: Print names of apicv inhibit reasons in
 traces



On 5/7/2024 4:23 AM, Alejandro Jimenez wrote:
> Use the tracing infrastructure helper __print_flags() for printing flag
> bitfields, to enhance the trace output by displaying a string describing
> each of the inhibit reasons set.
> 
> The kvm_apicv_inhibit_changed tracepoint currently shows the raw bitmap
> value, requiring the user to consult the source file where the inhibit
> reasons are defined to decode the trace output.
> 
> Co-developed-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>

Looks good to me.

Reviewed-by: Vasant Hegde <vasant.hegde@....com>

-Vasant

> ---
>  arch/x86/include/asm/kvm_host.h | 19 +++++++++++++++++++
>  arch/x86/kvm/trace.h            |  9 +++++++--
>  arch/x86/kvm/x86.c              |  4 ++++
>  3 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1d13e3cd1dc5..08f83efd12ff 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1273,8 +1273,27 @@ enum kvm_apicv_inhibit {
>  	 * mapping between logical ID and vCPU.
>  	 */
>  	APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED,
> +
> +	NR_APICV_INHIBIT_REASONS,
>  };
>  
> +#define __APICV_INHIBIT_REASON(reason)			\
> +	{ BIT(APICV_INHIBIT_REASON_##reason), #reason }
> +
> +#define APICV_INHIBIT_REASONS				\
> +	__APICV_INHIBIT_REASON(DISABLE),		\
> +	__APICV_INHIBIT_REASON(HYPERV),			\
> +	__APICV_INHIBIT_REASON(ABSENT),			\
> +	__APICV_INHIBIT_REASON(BLOCKIRQ),		\
> +	__APICV_INHIBIT_REASON(PHYSICAL_ID_ALIASED),	\
> +	__APICV_INHIBIT_REASON(APIC_ID_MODIFIED),	\
> +	__APICV_INHIBIT_REASON(APIC_BASE_MODIFIED),	\
> +	__APICV_INHIBIT_REASON(NESTED),			\
> +	__APICV_INHIBIT_REASON(IRQWIN),			\
> +	__APICV_INHIBIT_REASON(PIT_REINJ),		\
> +	__APICV_INHIBIT_REASON(SEV),			\
> +	__APICV_INHIBIT_REASON(LOGICAL_ID_ALIASED)
> +
>  struct kvm_arch {
>  	unsigned long n_used_mmu_pages;
>  	unsigned long n_requested_mmu_pages;
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index 9d0b02ef307e..f23fb9a6776e 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -1375,6 +1375,10 @@ TRACE_EVENT(kvm_hv_stimer_cleanup,
>  		  __entry->vcpu_id, __entry->timer_index)
>  );
>  
> +#define kvm_print_apicv_inhibit_reasons(inhibits)	\
> +	(inhibits), (inhibits) ? " " : "",		\
> +	(inhibits) ? __print_flags(inhibits, "|", APICV_INHIBIT_REASONS) : ""
> +
>  TRACE_EVENT(kvm_apicv_inhibit_changed,
>  	    TP_PROTO(int reason, bool set, unsigned long inhibits),
>  	    TP_ARGS(reason, set, inhibits),
> @@ -1391,9 +1395,10 @@ TRACE_EVENT(kvm_apicv_inhibit_changed,
>  		__entry->inhibits = inhibits;
>  	),
>  
> -	TP_printk("%s reason=%u, inhibits=0x%lx",
> +	TP_printk("%s reason=%u, inhibits=0x%lx%s%s",
>  		  __entry->set ? "set" : "cleared",
> -		  __entry->reason, __entry->inhibits)
> +		  __entry->reason,
> +		  kvm_print_apicv_inhibit_reasons(__entry->inhibits))
>  );
>  
>  TRACE_EVENT(kvm_apicv_accept_irq,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b389129d59a9..597ff748f955 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10011,6 +10011,10 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_apicv_activated);
>  static void set_or_clear_apicv_inhibit(unsigned long *inhibits,
>  				       enum kvm_apicv_inhibit reason, bool set)
>  {
> +	const struct trace_print_flags apicv_inhibits[] = { APICV_INHIBIT_REASONS };
> +
> +	BUILD_BUG_ON(ARRAY_SIZE(apicv_inhibits) != NR_APICV_INHIBIT_REASONS);
> +
>  	if (set)
>  		__set_bit(reason, inhibits);
>  	else