linux-kernel - Re: [PATCH v2 06/13] KVM: x86: Refactor emulate tracepoint to explicitly take context

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Message-ID: <8736axjmte.fsf@vitty.brq.redhat.com>
Date:   Wed, 26 Feb 2020 18:11:25 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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 v2 06/13] KVM: x86: Refactor emulate tracepoint to explicitly take context

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

> Explicitly pass the emulation context to the emulate tracepoint in
> preparation of dynamically allocation the emulation context.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/trace.h | 22 +++++++++++-----------
>  arch/x86/kvm/x86.c   | 13 ++++++++-----
>  2 files changed, 19 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index f194dd058470..5605000ca5f6 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -731,8 +731,9 @@ TRACE_EVENT(kvm_skinit,
>  	})
>  
>  TRACE_EVENT(kvm_emulate_insn,
> -	TP_PROTO(struct kvm_vcpu *vcpu, __u8 failed),
> -	TP_ARGS(vcpu, failed),
> +	TP_PROTO(struct kvm_vcpu *vcpu, struct x86_emulate_ctxt *ctxt,
> +		 __u8 failed),
> +	TP_ARGS(vcpu, ctxt, failed),
>  
>  	TP_STRUCT__entry(
>  		__field(    __u64, rip                       )
> @@ -745,13 +746,10 @@ TRACE_EVENT(kvm_emulate_insn,
>  
>  	TP_fast_assign(
>  		__entry->csbase = kvm_x86_ops->get_segment_base(vcpu, VCPU_SREG_CS);

This seems the only usage of 'vcpu' parameter now; I checked and even
after switching to dynamic emulation context allocation we still set
ctxt->vcpu in alloc_emulate_ctxt(), can we get rid of 'vcpu' parameter
here then (and use ctxt->vcpu instead)?

> -		__entry->len = vcpu->arch.emulate_ctxt.fetch.ptr
> -			       - vcpu->arch.emulate_ctxt.fetch.data;
> -		__entry->rip = vcpu->arch.emulate_ctxt._eip - __entry->len;
> -		memcpy(__entry->insn,
> -		       vcpu->arch.emulate_ctxt.fetch.data,
> -		       15);
> -		__entry->flags = kei_decode_mode(vcpu->arch.emulate_ctxt.mode);
> +		__entry->len = ctxt->fetch.ptr - ctxt->fetch.data;
> +		__entry->rip = ctxt->_eip - __entry->len;
> +		memcpy(__entry->insn, ctxt->fetch.data, 15);
> +		__entry->flags = kei_decode_mode(ctxt->mode);
>  		__entry->failed = failed;
>  		),
>  
> @@ -764,8 +762,10 @@ TRACE_EVENT(kvm_emulate_insn,
>  		)
>  	);
>  
> -#define trace_kvm_emulate_insn_start(vcpu) trace_kvm_emulate_insn(vcpu, 0)
> -#define trace_kvm_emulate_insn_failed(vcpu) trace_kvm_emulate_insn(vcpu, 1)
> +#define trace_kvm_emulate_insn_start(vcpu, ctxt)	\
> +	trace_kvm_emulate_insn(vcpu, ctxt, 0)
> +#define trace_kvm_emulate_insn_failed(vcpu, ctxt)	\
> +	trace_kvm_emulate_insn(vcpu, ctxt, 1)
>  
>  TRACE_EVENT(
>  	vcpu_match_mmio,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 79d1113ad6e7..69d3dd64d90c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6460,10 +6460,13 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
>  }
>  EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt);
>  
> -static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
> +static int handle_emulation_failure(struct x86_emulate_ctxt *ctxt,
> +				    int emulation_type)
>  {
> +	struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
> +
>  	++vcpu->stat.insn_emulation_fail;
> -	trace_kvm_emulate_insn_failed(vcpu);
> +	trace_kvm_emulate_insn_failed(vcpu, ctxt);
>  
>  	if (emulation_type & EMULTYPE_VMWARE_GP) {
>  		kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
> @@ -6788,7 +6791,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  
>  		r = x86_decode_insn(ctxt, insn, insn_len);
>  
> -		trace_kvm_emulate_insn_start(vcpu);
> +		trace_kvm_emulate_insn_start(vcpu, ctxt);
>  		++vcpu->stat.insn_emulation;
>  		if (r != EMULATION_OK)  {
>  			if ((emulation_type & EMULTYPE_TRAP_UD) ||
> @@ -6810,7 +6813,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  				inject_emulated_exception(ctxt);
>  				return 1;
>  			}
> -			return handle_emulation_failure(vcpu, emulation_type);
> +			return handle_emulation_failure(ctxt, emulation_type);
>  		}
>  	}
>  
> @@ -6856,7 +6859,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  					emulation_type))
>  			return 1;
>  
> -		return handle_emulation_failure(vcpu, emulation_type);
> +		return handle_emulation_failure(ctxt, emulation_type);
>  	}
>  
>  	if (ctxt->have_exception) {

-- 
Vitaly