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41 | Wed, 14 Oct 2015 19:33:12 -0300 | |
42 | Date: Wed, 14 Oct 2015 19:33:09 -0300 | |
43 | From: Marcelo Tosatti <mtosatti@redhat.com> | |
44 | To: kvm@vger.kernel.org | |
45 | Cc: Rik van Riel <riel@redhat.com>, | |
46 | "Dr. David Alan Gilbert" <dgilbert@redhat.com>, | |
47 | Paolo Bonzini <pbonzini@redhat.com>, | |
48 | Amit Shah <amit.shah@redhat.com> | |
49 | Subject: [PATCH] KVM: x86: move steal time initialization to vcpu entry time | |
50 | Message-ID: <20151014223309.GA13900@amt.cnet> | |
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56 | Sender: kvm-owner@vger.kernel.org | |
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58 | List-ID: <kvm.vger.kernel.org> | |
59 | X-Mailing-List: kvm@vger.kernel.org | |
60 | ||
61 | ||
62 | As reported at https://bugs.launchpad.net/qemu/+bug/1494350, | |
63 | it is possible to have vcpu->arch.st.last_steal initialized | |
64 | from a thread other than vcpu thread, say the iothread, via | |
65 | KVM_SET_MSRS. | |
66 | ||
67 | Which can cause an overflow later (when subtracting from vcpu threads | |
68 | sched_info.run_delay). | |
69 | ||
70 | To avoid that, move steal time accumulation to vcpu entry time, | |
71 | before copying steal time data to guest. | |
72 | ||
73 | Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> | |
74 | ||
75 | diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c | |
76 | index 8f0f6ec..0e0332e 100644 | |
77 | --- a/arch/x86/kvm/x86.c | |
78 | +++ b/arch/x86/kvm/x86.c | |
79 | @@ -2030,6 +2030,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu) | |
80 | ||
81 | static void record_steal_time(struct kvm_vcpu *vcpu) | |
82 | { | |
83 | + accumulate_steal_time(vcpu); | |
84 | + | |
85 | if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) | |
86 | return; | |
87 | ||
88 | @@ -2182,12 +2184,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) | |
89 | if (!(data & KVM_MSR_ENABLED)) | |
90 | break; | |
91 | ||
92 | - vcpu->arch.st.last_steal = current->sched_info.run_delay; | |
93 | - | |
94 | - preempt_disable(); | |
95 | - accumulate_steal_time(vcpu); | |
96 | - preempt_enable(); | |
97 | - | |
98 | kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); | |
99 | ||
100 | break; | |
101 | @@ -2830,7 +2826,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) | |
102 | vcpu->cpu = cpu; | |
103 | } | |
104 | ||
105 | - accumulate_steal_time(vcpu); | |
106 | kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); | |
107 | } | |
108 | ||
109 | -- | |
110 | To unsubscribe from this list: send the line "unsubscribe kvm" in | |
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