From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752822AbeDJMEI (ORCPT ); Tue, 10 Apr 2018 08:04:08 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54720 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752541AbeDJMEG (ORCPT ); Tue, 10 Apr 2018 08:04:06 -0400 Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint To: Eduardo Habkost , Wanpeng Li Cc: LKML , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Peter Zijlstra References: <1518185725-69559-1-git-send-email-wanpengli@tencent.com> <20180309141653.GA2871@localhost.localdomain> <20180410115711.GE29865@localhost.localdomain> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; prefer-encrypt=mutual; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0f UGFvbG8gQm9uemluaSA8Ym9uemluaUBnbnUub3JnPsLBTQQTAQIAIwUCVEJ7AwIbAwcLCQgH AwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEH4VEAzNNmmxNcwOniaZVLsuy1lW/ntYCA0Caz0i sHpmecK8aWlvL9wpQCk4GlOX9L1emyYXZPmzIYB0IRqmSzAlZxi+A2qm9XOxs5gJ2xqMEXX5 FMtUH3kpkWWJeLqe7z0EoQdUI4EG988uv/tdZyqjUn2XJE+K01x7r3MkUSFz/HZKZiCvYuze VlS0NTYdUt5jBXualvAwNKfxEkrxeHjxgdFHjYWhjflahY7TNRmuqPM/Lx7wAuyoDjlYNE40 Z+Kun4/KjMbjgpcF4Nf3PJQR8qXI6p3so2qsSn91tY7DFSJO6v2HwFJkC2jU95wxfNmTEUZc znXahYbVOwCDJRuPrE5GKFd/XJU9u5hNtr/uYipHij01WXal2cce1S5mn1/HuM1yo1u8xdHy IupCd57EWI948e8BlhpujUCU2tzOb2iYS0kpmJ9/oLVZrOcSZCcCl2P0AaCAsj59z2kwQS9D du0WxUs8waso0Qq6tDEHo8yLCOJDzSz4oojTtWe4zsulVnWV+wu70AioemAT8S6JOtlu60C5 dHgQUD1Tp+ReXpDKXmjbASJx4otvW0qah3o6JaqO79tbDqIvncu3tewwp6c85uZd48JnIOh3 utBAu684nJakbbvZUGikJfxd887ATQRUQnHuAQgAx4dxXO6/Zun0eVYOnr5GRl76+2UrAAem Vv9Yfn2PbDIbxXqLff7oyVJIkw4WdhQIIvvtu5zH24iYjmdfbg8iWpP7NqxUQRUZJEWbx2CR wkMHtOmzQiQ2tSLjKh/cHeyFH68xjeLcinR7jXMrHQK+UCEw6jqi1oeZzGvfmxarUmS0uRuf fAb589AJW50kkQK9VD/9QC2FJISSUDnRC0PawGSZDXhmvITJMdD4TjYrePYhSY4uuIV02v02 8TVAaYbIhxvDY0hUQE4r8ZbGRLn52bEzaIPgl1p/adKfeOUeMReg/CkyzQpmyB1TSk8lDMxQ zCYHXAzwnGi8WU9iuE1P0wARAQABwsEzBBgBAgAJBQJUQnHuAhsMAAoJEH4VEAzNNmmxp1EO oJy0uZggJm7gZKeJ7iUpeX4eqUtqelUw6gU2daz2hE/jsxsTbC/w5piHmk1H1VWDKEM4bQBT uiJ0bfo55SWsUNN+c9hhIX+Y8LEe22izK3w7mRpvGcg+/ZRG4DEMHLP6JVsv5GMpoYwYOmHn plOzCXHvmdlW0i6SrMsBDl9rw4AtIa6bRwWLim1lQ6EM3PWifPrWSUPrPcw4OLSwFk0CPqC4 HYv/7ZnASVkR5EERFF3+6iaaVi5OgBd81F1TCvCX2BEyIDRZLJNvX3TOd5FEN+lIrl26xecz 876SvcOb5SL5SKg9/rCBufdPSjojkGFWGziHiFaYhbuI2E+NfWLJtd+ZvWAAV+O0d8vFFSvr iy9enJ8kxJwhC0ECbSKFY+W1eTIhMD3aeAKY90drozWEyHhENf4l/V+Ja5vOnW+gCDQkGt2Y 1lJAPPSIqZKvHzGShdh8DduC0U3xYkfbGAUvbxeepjgzp0uEnBXfPTy09JGpgWbg0w91GyfT /ujKaGd4vxG2Ei+MMNDmS1SMx7wu0evvQ5kT9NPzyq8R2GIhVSiAd2jioGuTjX6AZCFv3ToO 53DliFMkVTecLptsXaesuUHgL9dKIfvpm+rNXRn9wAwGjk0X/A== Message-ID: <951766c8-3cac-af10-e63d-ea96aa99fa1b@redhat.com> Date: Tue, 10 Apr 2018 14:04:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180410115711.GE29865@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/04/2018 13:57, Eduardo Habkost wrote: > On Tue, Apr 10, 2018 at 05:13:21PM +0800, Wanpeng Li wrote: >> Hi Eduardo, >> 2018-03-09 22:16 GMT+08:00 Eduardo Habkost : >>> On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote: >>>> From: Wanpeng Li >>>> >>>> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit >>>> to determine if they run on dedicated vCPUs, allowing optimizations such >>>> as usage of qspinlocks. >>>> >>>> Cc: Paolo Bonzini >>>> Cc: Radim Krčmář >>>> Cc: Eduardo Habkost >>>> Signed-off-by: Wanpeng Li >>>> --- >>>> v1 -> v2: >>>> * add a new feature word >>>> >>>> target/i386/cpu.c | 14 ++++++++++++++ >>>> target/i386/cpu.h | 3 +++ >>>> target/i386/kvm.c | 4 ++++ >>>> 3 files changed, 21 insertions(+) >>>> >>>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c >>>> index d70954b..e2974ad 100644 >>>> --- a/target/i386/cpu.c >>>> +++ b/target/i386/cpu.c >>>> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = { >>>> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX, >>>> .tcg_features = TCG_KVM_FEATURES, >>>> }, >>>> + [FEAT_KVM_HINTS] = { >>>> + .feat_names = { >>>> + "hint-dedicated", NULL, NULL, NULL, >>> >>> I suggest naming it "kvm-hint-dedicated", to indicate it's >>> KVM-specific. >> >> I found this feature is enabled by default w/o kvm-hint-dedicated >> parameter, any idea how to make it disabled by default? > > You mean on "-cpu host", right? > > The assumption in most of the code is that anything enabled on > GET_SUPPORTED_CPUID should be enabled on "-cpu host". This > shouldn't be the case for FEAT_KVM_HINTS. > > Untested fix below. > > Signed-off-by: Eduardo Habkost > --- > target/i386/cpu.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 1a6b082b6f..a20fe26573 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -295,6 +295,8 @@ typedef struct FeatureWordInfo { > uint32_t tcg_features; /* Feature flags supported by TCG */ > uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */ > uint32_t migratable_flags; /* Feature flags known to be migratable */ > + /* Features that shouldn't be auto-enabled by "-cpu host" */ > + uint32_t no_autoenable_flags; > } FeatureWordInfo; > > static FeatureWordInfo feature_word_info[FEATURE_WORDS] = { > @@ -400,6 +402,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = { > }, > .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX, > .tcg_features = TCG_KVM_FEATURES, > + /* > + * KVM hints aren't auto-enabled by -cpu host, they need to be > + * explicitly enabled in the command-line. > + */ > + .no_autoenable_flags = ~0U, > }, > [FEAT_HYPERV_EAX] = { > .feat_names = { > @@ -4062,7 +4069,8 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp) > */ > env->features[w] |= > x86_cpu_get_supported_feature_word(w, cpu->migratable) & > - ~env->user_features[w]; > + ~env->user_features[w] & \ > + ~feature_word_info[w].no_autoenable_flags; > } > } > > Reviewed-by: Paolo Bonzini