From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eduardo Habkost Subject: [PATCH v3 2/2] kvm: Allow invtsc migration if tsc-khz is set explicitly Date: Sun, 8 Jan 2017 15:32:34 -0200 Message-ID: <20170108173234.25721-3-ehabkost@redhat.com> References: <20170108173234.25721-1-ehabkost@redhat.com> Cc: Marcelo Tosatti , Paolo Bonzini , kvm@vger.kernel.org, Haozhong Zhang To: qemu-devel@nongnu.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51252 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753910AbdAHRco (ORCPT ); Sun, 8 Jan 2017 12:32:44 -0500 In-Reply-To: <20170108173234.25721-1-ehabkost@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: We can safely allow a VM to be migrated with invtsc enabled if tsc-khz is set explicitly, because: * QEMU already refuses to start if it can't set the TSC frequency to the configured value. * Management software is already required to keep device configuration (including CPU configuration) the same on migration source and destination. Signed-off-by: Eduardo Habkost --- Changes v1 -> v2: * Reworded commit message Changes v2 -> v3: * Fixed build failure --- target/i386/kvm.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/target/i386/kvm.c b/target/i386/kvm.c index a26290fdc1..abb5a41983 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -962,15 +962,17 @@ int kvm_arch_init_vcpu(CPUState *cs) has_msr_mcg_ext_ctl = has_msr_feature_control = true; } - if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) && - invtsc_mig_blocker == NULL) { - /* for migration */ - error_setg(&invtsc_mig_blocker, - "State blocked by non-migratable CPU device" - " (invtsc flag)"); - migrate_add_blocker(invtsc_mig_blocker); - /* for savevm */ - vmstate_x86_cpu.unmigratable = 1; + if (!env->user_tsc_khz) { + if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) && + invtsc_mig_blocker == NULL) { + /* for migration */ + error_setg(&invtsc_mig_blocker, + "State blocked by non-migratable CPU device" + " (invtsc flag)"); + migrate_add_blocker(invtsc_mig_blocker); + /* for savevm */ + vmstate_x86_cpu.unmigratable = 1; + } } cpuid_data.cpuid.padding = 0; -- 2.11.0.259.g40922b1