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

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Date:   Tue, 3 Mar 2020 18:29:30 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     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

On 03/03/20 17:48, Sean Christopherson wrote:
>>>  	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)?
> Hmm, ya, not sure what I was thinking here.
> 

As long as we have one use of vcpu, I'd rather skip this patch and
adjust patch 8 to use "->".  Even the other "explicitly take context"
parts are kinda debatable since you still have to do emul_to_vcpu.
Throwing a handful of

- 	struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
+ 	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;

into patch 8 is not bad at all and limits the churn.

Paolo