linux-kernel - Re: [PATCH] KVM: x86: Print symbolic names of VMX VM-Exit flags in traces

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Message-ID: <87sgicpnd0.fsf@vitty.brq.redhat.com>
Date:   Fri, 13 Mar 2020 11:20:43 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Print symbolic names of VMX VM-Exit flags in traces

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> Use __print_flags() to display the names of VMX flags in VM-Exit traces
> and strip the flags when printing the basic exit reason, e.g. so that a
> failed VM-Entry due to invalid guest state gets recorded as
> "INVALID_STATE FAILED_VMENTRY" instead of "0x80000021".
>
> Opportunstically fix misaligned variables in the kvm_exit and
> kvm_nested_vmexit_inject tracepoints.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/include/uapi/asm/vmx.h |  3 +++
>  arch/x86/kvm/trace.h            | 32 +++++++++++++++++---------------
>  2 files changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
> index e95b72ec19bc..b8ff9e8ac0d5 100644
> --- a/arch/x86/include/uapi/asm/vmx.h
> +++ b/arch/x86/include/uapi/asm/vmx.h
> @@ -150,6 +150,9 @@
>  	{ EXIT_REASON_UMWAIT,                "UMWAIT" }, \
>  	{ EXIT_REASON_TPAUSE,                "TPAUSE" }
>  
> +#define VMX_EXIT_REASON_FLAGS \
> +	{ VMX_EXIT_REASONS_FAILED_VMENTRY,	"FAILED_VMENTRY" }
> +
>  #define VMX_ABORT_SAVE_GUEST_MSR_FAIL        1
>  #define VMX_ABORT_LOAD_HOST_PDPTE_FAIL       2
>  #define VMX_ABORT_LOAD_HOST_MSR_FAIL         4
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index f5b8814d9f83..3cfc8d97b158 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -219,6 +219,14 @@ TRACE_EVENT(kvm_apic,
>  #define KVM_ISA_VMX   1
>  #define KVM_ISA_SVM   2
>  
> +#define kvm_print_exit_reason(exit_reason, isa)				\
> +	(isa == KVM_ISA_VMX) ?						\
> +	__print_symbolic(exit_reason & 0xffff, VMX_EXIT_REASONS) :	\
> +	__print_symbolic(exit_reason, SVM_EXIT_REASONS),		\
> +	(isa == KVM_ISA_VMX && exit_reason & ~0xffff) ? " " : "",	\
> +	(isa == KVM_ISA_VMX) ?						\
> +	__print_flags(exit_reason & ~0xffff, " ", VMX_EXIT_REASON_FLAGS) : ""
> +
>  /*
>   * Tracepoint for kvm guest exit:
>   */
> @@ -244,12 +252,10 @@ TRACE_EVENT(kvm_exit,
>  					   &__entry->info2);
>  	),
>  
> -	TP_printk("vcpu %u reason %s rip 0x%lx info %llx %llx",
> +	TP_printk("vcpu %u reason %s%s%s rip 0x%lx info %llx %llx",
>  		  __entry->vcpu_id,
> -		 (__entry->isa == KVM_ISA_VMX) ?
> -		 __print_symbolic(__entry->exit_reason, VMX_EXIT_REASONS) :
> -		 __print_symbolic(__entry->exit_reason, SVM_EXIT_REASONS),
> -		 __entry->guest_rip, __entry->info1, __entry->info2)
> +		  kvm_print_exit_reason(__entry->exit_reason, __entry->isa),
> +		  __entry->guest_rip, __entry->info1, __entry->info2)
>  );
>  
>  /*
> @@ -582,12 +588,10 @@ TRACE_EVENT(kvm_nested_vmexit,
>  		__entry->exit_int_info_err	= exit_int_info_err;
>  		__entry->isa			= isa;

Unrelated to your patch, just a random thought: I *think* it would be
possible to avoid passing 'isa' to these tracepoints and figure out
which module is embedding them instead (THIS_MODULE/KBUILD_MODNAME/...
magic or something like that) but it may not worth the effort.

>  	),
> -	TP_printk("rip: 0x%016llx reason: %s ext_inf1: 0x%016llx "
> +	TP_printk("rip: 0x%016llx reason: %s%s%s ext_inf1: 0x%016llx "
>  		  "ext_inf2: 0x%016llx ext_int: 0x%08x ext_int_err: 0x%08x",
>  		  __entry->rip,
> -		 (__entry->isa == KVM_ISA_VMX) ?
> -		 __print_symbolic(__entry->exit_code, VMX_EXIT_REASONS) :
> -		 __print_symbolic(__entry->exit_code, SVM_EXIT_REASONS),
> +		  kvm_print_exit_reason(__entry->exit_code, __entry->isa),
>  		  __entry->exit_info1, __entry->exit_info2,
>  		  __entry->exit_int_info, __entry->exit_int_info_err)
>  );
> @@ -620,13 +624,11 @@ TRACE_EVENT(kvm_nested_vmexit_inject,
>  		__entry->isa			= isa;
>  	),
>  
> -	TP_printk("reason: %s ext_inf1: 0x%016llx "
> +	TP_printk("reason: %s%s%s ext_inf1: 0x%016llx "
>  		  "ext_inf2: 0x%016llx ext_int: 0x%08x ext_int_err: 0x%08x",
> -		 (__entry->isa == KVM_ISA_VMX) ?
> -		 __print_symbolic(__entry->exit_code, VMX_EXIT_REASONS) :
> -		 __print_symbolic(__entry->exit_code, SVM_EXIT_REASONS),
> -		__entry->exit_info1, __entry->exit_info2,
> -		__entry->exit_int_info, __entry->exit_int_info_err)
> +		  kvm_print_exit_reason(__entry->exit_code, __entry->isa),
> +		  __entry->exit_info1, __entry->exit_info2,
> +		  __entry->exit_int_info, __entry->exit_int_info_err)
>  );
>  
>  /*

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly