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

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Date: Mon, 8 Apr 2024 14:13:14 +0530
From: Vasant Hegde <vashegde@....com>
To: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>, kvm@...r.kernel.org
Cc: seanjc@...gle.com, 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 1/1] KVM: x86: Print names of apicv inhibit reasons in
 traces

On 2/15/2024 4:05 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 inhbit
> reasons are defined to decode the trace output.
> 
> Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>

I have reviewed and tested this patch on AMD Genoa system. It looks good 
to me.

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

-Vasant

> 
> ---
> checkpatch reports an error:
> ERROR: Macros with complex values should be enclosed in parentheses
> 
> but that seems common for other patches that also use a macro to define an array
> of struct trace_print_flags used by __print_flags().
> 
> I did not include an example of the new traces in the commit message since they
> are longer than 80 columns, but perhaps that is desirable. e.g.:
> 
> qemu-system-x86-6961    [055] .....  1779.344065: kvm_apicv_inhibit_changed: set reason=2, inhibits=0x4 ABSENT
> qemu-system-x86-6961    [055] .....  1779.356710: kvm_apicv_inhibit_changed: cleared reason=2, inhibits=0x0
> 
> qemu-system-x86-9912    [137] ..... 57106.196107: kvm_apicv_inhibit_changed: set reason=8, inhibits=0x300 IRQWIN|PIT_REINJ
> qemu-system-x86-9912    [137] ..... 57106.196115: kvm_apicv_inhibit_changed: cleared reason=8, inhibits=0x200 PIT_REINJ
> ---
>   arch/x86/kvm/trace.h | 28 ++++++++++++++++++++++++++--
>   1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index b82e6ed4f024..8469e59dfce2 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -1372,6 +1372,27 @@ TRACE_EVENT(kvm_hv_stimer_cleanup,
>   		  __entry->vcpu_id, __entry->timer_index)
>   );
>   
> +/*
> + * The inhibit flags in this flag array must be kept in sync with the
> + * kvm_apicv_inhibit enum members in <asm/kvm_host.h>.
> + */
> +#define APICV_INHIBIT_FLAGS \
> +	{ BIT(APICV_INHIBIT_REASON_DISABLE),		 "DISABLED" }, \
> +	{ BIT(APICV_INHIBIT_REASON_HYPERV),		 "HYPERV" }, \
> +	{ BIT(APICV_INHIBIT_REASON_ABSENT),		 "ABSENT" }, \
> +	{ BIT(APICV_INHIBIT_REASON_BLOCKIRQ),		 "BLOCKIRQ" }, \
> +	{ BIT(APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED), "PHYS_ID_ALIASED" }, \
> +	{ BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED),	 "APIC_ID_MOD" }, \
> +	{ BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED),	 "APIC_BASE_MOD" }, \
> +	{ BIT(APICV_INHIBIT_REASON_NESTED),		 "NESTED" }, \
> +	{ BIT(APICV_INHIBIT_REASON_IRQWIN),		 "IRQWIN" }, \
> +	{ BIT(APICV_INHIBIT_REASON_PIT_REINJ),		 "PIT_REINJ" }, \
> +	{ BIT(APICV_INHIBIT_REASON_SEV),		 "SEV" }, \
> +	{ BIT(APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED),	 "LOG_ID_ALIASED" } \
> +
> +#define show_inhibit_reasons(inhibits) \
> +	__print_flags(inhibits, "|", APICV_INHIBIT_FLAGS)
> +
>   TRACE_EVENT(kvm_apicv_inhibit_changed,
>   	    TP_PROTO(int reason, bool set, unsigned long inhibits),
>   	    TP_ARGS(reason, set, inhibits),
> @@ -1388,9 +1409,12 @@ 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, __entry->inhibits,
> +		  __entry->inhibits ? " " : "",
> +		  __entry->inhibits ?
> +		  show_inhibit_reasons(__entry->inhibits) : "")
>   );
>   
>   TRACE_EVENT(kvm_apicv_accept_irq,
> 
> base-commit: 7455665a3521aa7b56245c0a2810f748adc5fdd4