From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 06/13] KVM: x86: Refactor emulate tracepoint to explicitly take context
Date: Tue, 3 Mar 2020 09:42:42 -0800 [thread overview]
Message-ID: <20200303174242.GN1439@linux.intel.com> (raw)
In-Reply-To: <2f3f7aff-2bd0-fa62-4b66-9f90f125e44e@redhat.com>
On Tue, Mar 03, 2020 at 06:29:30PM +0100, Paolo Bonzini wrote:
> 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.
Hmm, I'd prefer to explicitly pass @ctxt, even for the tracepoint. I get
that it's technically unnecessary churn, but explicitly passing @ctxt means
that every funcition that grabs arch.emulate_ctxt (all three of 'em) checks
for a NULL ctxt. That makes it trivial to visually audit that there's no
risk of a bad pointer dereference, and IMO having @ctxt in the prototype
is helpful to see "oh, this helper is called from within the emulator".
next prev parent reply other threads:[~2020-03-03 17:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-18 23:29 [PATCH v2 00/13] KVM: x86: Allow userspace to disable the emulator Sean Christopherson
2020-02-18 23:29 ` [PATCH v2 01/13] KVM: x86: Refactor I/O emulation helpers to provide vcpu-only variant Sean Christopherson
2020-02-26 15:16 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 02/13] KVM: x86: Explicitly pass an exception struct to check_intercept Sean Christopherson
2020-02-18 23:29 ` [PATCH v2 03/13] KVM: x86: Move emulation-only helpers to emulate.c Sean Christopherson
2020-02-26 15:23 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 04/13] KVM: x86: Refactor R/W page helper to take the emulation context Sean Christopherson
2020-02-26 15:24 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 05/13] KVM: x86: Refactor emulated exception injection to take the emul context Sean Christopherson
2020-02-26 15:25 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 06/13] KVM: x86: Refactor emulate tracepoint to explicitly take context Sean Christopherson
2020-02-26 17:11 ` Vitaly Kuznetsov
2020-03-03 16:48 ` Sean Christopherson
2020-03-03 17:29 ` Paolo Bonzini
2020-03-03 17:42 ` Sean Christopherson [this message]
2020-03-03 17:44 ` Paolo Bonzini
2020-02-18 23:29 ` [PATCH v2 07/13] KVM: x86: Refactor init_emulate_ctxt() " Sean Christopherson
2020-02-26 17:13 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 08/13] KVM: x86: Dynamically allocate per-vCPU emulation context Sean Christopherson
2020-02-26 17:29 ` Vitaly Kuznetsov
2020-03-03 10:26 ` Paolo Bonzini
2020-03-03 14:57 ` Sean Christopherson
2020-03-03 16:18 ` Vitaly Kuznetsov
2020-03-03 16:52 ` Sean Christopherson
2020-02-18 23:29 ` [PATCH v2 09/13] KVM: x86: Move kvm_emulate.h into KVM's private directory Sean Christopherson
2020-02-26 17:38 ` Vitaly Kuznetsov
2020-03-03 10:27 ` Paolo Bonzini
2020-02-18 23:29 ` [PATCH v2 10/13] KVM: x86: Shrink the usercopy region of the emulation context Sean Christopherson
2020-02-26 17:51 ` Vitaly Kuznetsov
2020-03-02 18:40 ` Paolo Bonzini
2020-03-02 19:19 ` Sean Christopherson
2020-03-02 19:13 ` Sean Christopherson
2020-02-18 23:29 ` [PATCH v2 11/13] KVM: x86: Add helper to "handle" internal emulation error Sean Christopherson
2020-02-26 17:52 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 12/13] KVM: x86: Add variable to control existence of emulator Sean Christopherson
2020-02-26 18:01 ` Vitaly Kuznetsov
2020-02-18 23:29 ` [PATCH v2 13/13] KVM: x86: Allow userspace to disable the kernel's emulator Sean Christopherson
2020-03-02 18:42 ` [PATCH v2 00/13] KVM: x86: Allow userspace to disable the emulator Paolo Bonzini
2020-03-02 20:02 ` Sean Christopherson
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