linux-kernel - Re: [PATCH] kvm: x86: add trace event for pvclock updates

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Date:	Thu, 06 Nov 2014 11:53:09 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	David Matlack <dmatlack@...gle.com>, kvm@...r.kernel.org
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kvm: x86: add trace event for pvclock updates



On 05/11/2014 20:46, David Matlack wrote:
> The new trace event records:
>   * the id of vcpu being updated
>   * the pvclock_vcpu_time_info struct being written to guest memory
> 
> This is useful for debugging pvclock bugs, such as the bug fixed by
> "[PATCH] kvm: x86: Fix kvm clock versioning.".
> 
> Signed-off-by: David Matlack <dmatlack@...gle.com>
> ---
>  arch/x86/kvm/trace.h | 37 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c   |  2 ++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index 6b06ab8..c2a34bb 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -5,6 +5,7 @@
>  #include <asm/vmx.h>
>  #include <asm/svm.h>
>  #include <asm/clocksource.h>
> +#include <asm/pvclock-abi.h>
>  
>  #undef TRACE_SYSTEM
>  #define TRACE_SYSTEM kvm
> @@ -877,6 +878,42 @@ TRACE_EVENT(kvm_ple_window,
>  #define trace_kvm_ple_window_shrink(vcpu_id, new, old) \
>  	trace_kvm_ple_window(false, vcpu_id, new, old)
>  
> +TRACE_EVENT(kvm_pvclock_update,
> +	TP_PROTO(unsigned int vcpu_id, struct pvclock_vcpu_time_info *pvclock),
> +	TP_ARGS(vcpu_id, pvclock),
> +
> +	TP_STRUCT__entry(
> +		__field(	unsigned int,	vcpu_id			)
> +		__field(	__u32,		version			)
> +		__field(	__u64,		tsc_timestamp		)
> +		__field(	__u64,		system_time		)
> +		__field(	__u32,		tsc_to_system_mul	)
> +		__field(	__s8,		tsc_shift		)
> +		__field(	__u8,		flags			)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->vcpu_id	   = vcpu_id;
> +		__entry->version	   = pvclock->version;
> +		__entry->tsc_timestamp	   = pvclock->tsc_timestamp;
> +		__entry->system_time	   = pvclock->system_time;
> +		__entry->tsc_to_system_mul = pvclock->tsc_to_system_mul;
> +		__entry->tsc_shift	   = pvclock->tsc_shift;
> +		__entry->flags		   = pvclock->flags;
> +	),
> +
> +	TP_printk("vcpu_id %u, pvclock { version %u, tsc_timestamp 0x%llx, "
> +		  "system_time 0x%llx, tsc_to_system_mul 0x%x, tsc_shift %d, "
> +		  "flags 0x%x }",
> +		  __entry->vcpu_id,
> +		  __entry->version,
> +		  __entry->tsc_timestamp,
> +		  __entry->system_time,
> +		  __entry->tsc_to_system_mul,
> +		  __entry->tsc_shift,
> +		  __entry->flags)
> +);
> +
>  #endif /* _TRACE_KVM_H */
>  
>  #undef TRACE_INCLUDE_PATH
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0033df3..0f533df 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1662,6 +1662,8 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
>  
>  	vcpu->hv_clock.flags = pvclock_flags;
>  
> +	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);
> +
>  	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
>  				&vcpu->hv_clock,
>  				sizeof(vcpu->hv_clock));
> 

Applied, thanks.

Paolo
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