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From: Andrea Arcangeli <aarcange@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Peter Xu <peterx@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers
Date: Mon, 23 Sep 2019 19:43:07 -0400	[thread overview]
Message-ID: <20190923234307.GG19996@redhat.com> (raw)
In-Reply-To: <20190923212435.GO18195@linux.intel.com>

On Mon, Sep 23, 2019 at 02:24:35PM -0700, Sean Christopherson wrote:
> An extra CALL+RET isn't going to be noticeable, especially on modern
> hardware as the high frequency VMWRITE/VMREAD fields should hit the
> shadow VMCS.

In your last email with regard to the inlining optimizations made
possible by the monolithic KVM model you said "That'd likely save a
few CALL/RET/JMP instructions", that kind of directly contradicts the
above. I think neither one if taken at face value can be possibly
measured. However the above only is relevant for nested KVM so I'm
fine if there's an agreement that it's better to hide the nested vmx
handlers in nested.c at the cost of some call/ret.

From my part I'm dropping 15/16/17 in the short term, perhaps Vitaly
or you or Paolo if he has time, want to work on that part in parallel
to the orthogonal KVM monolithic changes?

Thanks,
Andrea

  reply	other threads:[~2019-09-23 23:43 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-20 21:24 [PATCH 00/17] KVM monolithic v1 Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 01/17] x86: spec_ctrl: fix SPEC_CTRL initialization after kexec Andrea Arcangeli
2019-09-23 10:22   ` Paolo Bonzini
2019-09-23 15:30     ` Sean Christopherson
2019-09-23 17:34       ` Andrea Arcangeli
2019-09-23 22:27         ` Sean Christopherson
2019-09-20 21:24 ` [PATCH 02/17] KVM: monolithic: x86: convert the kvm_x86_ops methods to external functions Andrea Arcangeli
2019-09-23 10:19   ` Paolo Bonzini
2019-09-23 16:13     ` Sean Christopherson
2019-09-23 16:51       ` Paolo Bonzini
2019-09-23 19:21     ` Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 03/17] KVM: monolithic: x86: handle the request_immediate_exit variation Andrea Arcangeli
2019-09-23 22:35   ` Sean Christopherson
2019-09-23 23:06     ` Andrea Arcangeli
2019-09-23 23:45       ` Sean Christopherson
2019-09-24  0:24         ` Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 04/17] KVM: monolithic: x86: convert the kvm_pmu_ops methods to external functions Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 05/17] KVM: monolithic: x86: enable the kvm_x86_ops " Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 06/17] KVM: monolithic: x86: enable the kvm_pmu_ops " Andrea Arcangeli
2019-09-20 21:24 ` [PATCH 07/17] KVM: monolithic: x86: adjust the section prefixes Andrea Arcangeli
2019-09-23 10:15   ` Paolo Bonzini
2019-09-25 12:13     ` Andrea Arcangeli
2019-09-25 12:32       ` Paolo Bonzini
2019-09-20 21:25 ` [PATCH 08/17] KVM: monolithic: adjust the section prefixes in the KVM common code Andrea Arcangeli
2019-09-20 21:25 ` [PATCH 09/17] KVM: monolithic: x86: remove kvm.ko Andrea Arcangeli
2019-09-20 21:25 ` [PATCH 10/17] KVM: monolithic: x86: use the external functions instead of kvm_x86_ops Andrea Arcangeli
2019-09-23 10:02   ` Paolo Bonzini
2019-09-20 21:25 ` [PATCH 11/17] KVM: monolithic: x86: remove exports Andrea Arcangeli
2019-09-20 21:25 ` [PATCH 12/17] KVM: monolithic: remove exports from KVM common code Andrea Arcangeli
2019-09-20 21:25 ` [PATCH 13/17] KVM: monolithic: x86: drop the kvm_pmu_ops structure Andrea Arcangeli
2019-09-23 10:21   ` Paolo Bonzini
2019-09-24  0:51     ` Andrea Arcangeli
2019-09-24  1:24       ` Paolo Bonzini
2019-09-20 21:25 ` [PATCH 14/17] KVM: monolithic: x86: inline more exit handlers in vmx.c Andrea Arcangeli
2019-09-23 10:19   ` Paolo Bonzini
2019-09-24  1:00     ` Andrea Arcangeli
2019-09-24  1:25       ` Paolo Bonzini
2019-09-24  1:55         ` Andrea Arcangeli
2019-09-24  2:56           ` Andrea Arcangeli
2019-09-25  7:52           ` Paolo Bonzini
2019-09-20 21:25 ` [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers Andrea Arcangeli
2019-09-23  9:31   ` Vitaly Kuznetsov
2019-09-23  9:57     ` Paolo Bonzini
2019-09-23 19:05       ` Andrea Arcangeli
2019-09-23 20:23         ` Sean Christopherson
2019-09-23 21:08           ` Andrea Arcangeli
2019-09-23 21:24             ` Sean Christopherson
2019-09-23 23:43               ` Andrea Arcangeli [this message]
2019-09-23 23:52                 ` Sean Christopherson
2019-09-24  0:16             ` Paolo Bonzini
2019-09-24  0:35               ` Sean Christopherson
2019-09-24  0:37                 ` Paolo Bonzini
2019-09-24  0:15           ` Paolo Bonzini
2019-09-24  0:38             ` Andrea Arcangeli
2019-09-24  0:46             ` Sean Christopherson
2019-09-24 21:46         ` Andrea Arcangeli
2019-09-25  7:50           ` Paolo Bonzini
2019-09-23 16:37     ` Sean Christopherson
2019-09-23 16:53       ` Paolo Bonzini
2019-09-23 17:42         ` Andrea Arcangeli
2019-09-23 18:15           ` Sean Christopherson
2019-09-23 19:12             ` Andrea Arcangeli
     [not found]     ` <E8FE7592-69C3-455E-8D80-A2D73BB2E14C@dinechin.org>
2019-09-25 20:51       ` Andrea Arcangeli
2019-09-23 16:28   ` Sean Christopherson
2019-09-20 21:25 ` [PATCH 16/17] KVM: retpolines: x86: eliminate retpoline from svm.c " Andrea Arcangeli
2019-09-23 10:01   ` Paolo Bonzini
2019-09-20 21:25 ` [PATCH 17/17] x86: retpolines: eliminate retpoline from msr event handlers Andrea Arcangeli
2019-09-23 15:39 ` [PATCH 00/17] KVM monolithic v1 Sean Christopherson

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