x86: vdso: fix pvclock races with task migration
commit 80f7fdb1 upstream. If we were migrated right after __getcpu, but before reading the migration_count, we wouldn't notice that we read TSC of a different VCPU, nor that KVM's bug made pvti invalid, as only migration_count on source VCPU is increased. Change vdso instead of updating migration_count on destination. Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Fixes: 0a4e6be9 ("x86: kvm: Revert "remove sched notifier for cross-cpu migrations"") Message-Id: <1428000263-11892-1-git-send-email-rkrcmar@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
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