1. A method for making a decision about virtual machine migration, comprising: receiving a migration request sent from a source host platform of a virtual machine to be migrated; performing security evaluation checks on the source host platform of the virtual machine to be migrated and on a target host platform of the virtual machine to be migrated according to the migration request, in order to obtain a first evaluation result of the source host platform and a second evaluation result of the target host platform; acquiring a third evaluation result of the virtual machine to be migrated, wherein the acquiring of the third evaluation result of the virtual machine to be migrated comprising: evaluating status information of the virtual machine to be migrated in order to obtain a status information evaluation result, wherein the evaluating the status information of the virtual machine to be migrated comprising: receiving an evaluation request sent from the target host platform, wherein the evaluation request carries evaluation requirements from the target host platform for the virtual machine to be migrated, and the evaluation requirements comprise mandatory evaluation attributes, and the mandatory evaluation attributes comprise owner of the virtual machine, use of the virtual machine, and information of historical host platforms of the virtual machine; acquiring information of attributes to be evaluated from the virtual machine to be migrated and the source host platform of the virtual machine to be migrated according to the evaluation requirements carried in the evaluation request; and obtaining the status information evaluation result according to a result obtained by comparing the required information of attributes to be evaluated and a corresponding evaluation standard, wherein the obtaining of the status information evaluation result comprising: determining whether the owner of the virtual machine to be migrated and an owner of a virtual machine that runs on the target host platform belong to the same owner group; if yes, determining that the evaluation for the mandatory evaluation attribute is passed; if no, determining that the evaluation is not passed; matching tasks that are performed by the virtual machine to be migrated and are acquired from the source host platform or the virtual machine to be migrated with types of task supported by the target host platform, and if the tasks that are performed by the virtual machine do match the types of task supported by the target host platform, determining that the evaluation for the mandatory evaluation attribute is passed; if the tasks that are performed by the virtual machine do not match the types of task supported by the target host platform, determining that the evaluation is not passed; matching information of a first historical host platform acquired from the source host platform with corresponding time logs of security events, and if there is no security event occurred when the virtual machine to be migrated is running on each historical host platform, or if there is a security event occurred when the virtual machine to be migrated is running on a historical host platform, and the security level of the occurred security event is in a scope of the security level of the security event of the target host platform; determining that the evaluation for the mandatory evaluation attribute is passed; if the security level of the occurred security event is not in a scope of the security level of the security event of the target host platform, determining that the evaluation is not passed; determining that the status information evaluation is passed if the evaluations for the mandatory evaluation attributes are all passed; determining that the status information evaluation is not passed if the evaluations for the mandatory evaluation attributes are not all passed; and returning a corresponding migration decision-making result to the source host platform according to the first evaluation result, the second evaluation result, and the third evaluation result, wherein the corresponding migration decision-making result indicates whether the virtual machine is permitted to be migrated from the source host platform to the target host platform.