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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2015-10-14 19:33:09 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-16 08:41:36 -0700 |
| commit | 73c1d981f04cdee52466ea0e5fc0d04c76ad6f49 (patch) | |
| tree | 97c65713d59a0fc77605846d4cdaafd7394faef4 | |
| parent | b4f8295ef4516a699997649894ff3a62f4d151d6 (diff) | |
| download | lwn-73c1d981f04cdee52466ea0e5fc0d04c76ad6f49.tar.gz lwn-73c1d981f04cdee52466ea0e5fc0d04c76ad6f49.zip | |
KVM: x86: move steal time initialization to vcpu entry time
commit 7cae2bedcbd4680b155999655e49c27b9cf020fa upstream.
As reported at https://bugs.launchpad.net/qemu/+bug/1494350,
it is possible to have vcpu->arch.st.last_steal initialized
from a thread other than vcpu thread, say the iothread, via
KVM_SET_MSRS.
Which can cause an overflow later (when subtracting from vcpu threads
sched_info.run_delay).
To avoid that, move steal time accumulation to vcpu entry time,
before copying steal time data to guest.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kvm/x86.c | 9 |
1 files changed, 2 insertions, 7 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 41ba726c1ce2..7f2b6dec4b2b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1941,6 +1941,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu) static void record_steal_time(struct kvm_vcpu *vcpu) { + accumulate_steal_time(vcpu); + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) return; @@ -2074,12 +2076,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (!(data & KVM_MSR_ENABLED)) break; - vcpu->arch.st.last_steal = current->sched_info.run_delay; - - preempt_disable(); - accumulate_steal_time(vcpu); - preempt_enable(); - kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); break; @@ -2758,7 +2754,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) vcpu->cpu = cpu; } - accumulate_steal_time(vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); } |