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([2001:b07:6468:f312:69b4:4715:609f:385f]) by smtp.gmail.com with ESMTPSA id s80sm3702185wme.41.2020.09.18.01.38.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Sep 2020 01:38:27 -0700 (PDT) Subject: Re: [PATCH] target/i386: always create kvmclock device To: Vitaly Kuznetsov , qemu-devel@nongnu.org References: <20200917111306.819263-1-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: <8783874f-8d6d-b1b6-20c3-9910c267779b@redhat.com> Date: Fri, 18 Sep 2020 10:38:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200917111306.819263-1-vkuznets@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/18 01:32:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.997, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Antoine Damhet , Marcelo Tosatti , Eduardo Habkost , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17/09/20 13:13, Vitaly Kuznetsov wrote: > QEMU's kvmclock device is only created when KVM PV feature bits for > kvmclock (KVM_FEATURE_CLOCKSOURCE/KVM_FEATURE_CLOCKSOURCE2) are > exposed to the guest. With 'kvm=off' cpu flag the device is not > created and we don't call KVM_GET_CLOCK/KVM_SET_CLOCK upon migration. > It was reported that without these call at least Hyper-V TSC page > clocksouce (which can be enabled independently) gets broken after > migration. > > Switch to creating kvmclock QEMU device unconditionally, it seems > to always make sense to call KVM_GET_CLOCK/KVM_SET_CLOCK on migration. > Use KVM_CAP_ADJUST_CLOCK check instead of CPUID feature bits. > > Reported-by: Antoine Damhet > Suggested-by: Paolo Bonzini > Signed-off-by: Vitaly Kuznetsov > --- > hw/i386/kvm/clock.c | 6 +----- > target/i386/kvm.c | 5 +++++ > target/i386/kvm_i386.h | 1 + > 3 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c > index 64283358f91d..526c9ea5172b 100644 > --- a/hw/i386/kvm/clock.c > +++ b/hw/i386/kvm/clock.c > @@ -330,11 +330,7 @@ static const TypeInfo kvmclock_info = { > /* Note: Must be called after VCPU initialization. */ > void kvmclock_create(void) > { > - X86CPU *cpu = X86_CPU(first_cpu); > - > - if (kvm_enabled() && > - cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) | > - (1ULL << KVM_FEATURE_CLOCKSOURCE2))) { > + if (kvm_enabled() && kvm_has_adjust_clock()) { > sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL); > } > } > diff --git a/target/i386/kvm.c b/target/i386/kvm.c > index 4a8b3a41c1bc..20b31b65307b 100644 > --- a/target/i386/kvm.c > +++ b/target/i386/kvm.c > @@ -143,6 +143,11 @@ bool kvm_has_adjust_clock_stable(void) > return (ret == KVM_CLOCK_TSC_STABLE); > } > > +bool kvm_has_adjust_clock(void) > +{ > + return kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK); > +} > + > bool kvm_has_exception_payload(void) > { > return has_exception_payload; > diff --git a/target/i386/kvm_i386.h b/target/i386/kvm_i386.h > index 064b8798a26c..0fce4e51d2d6 100644 > --- a/target/i386/kvm_i386.h > +++ b/target/i386/kvm_i386.h > @@ -34,6 +34,7 @@ > > bool kvm_allows_irq0_override(void); > bool kvm_has_smm(void); > +bool kvm_has_adjust_clock(void); > bool kvm_has_adjust_clock_stable(void); > bool kvm_has_exception_payload(void); > void kvm_synchronize_all_tsc(void); > Queued, thanks. Paolo