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This patch adds more check in SmmIsBufferOutsideSmmValid(), to make sure that SMM communication buffer is only EfiReservedMemoryType/EfiRuntimeServicesCode/ EfiRuntimeServicesData/EfiACPIMemoryNVS. So that the communication buffer will not touch any OS memory. The assumption is that a platform reports valid SMM communication buffer at EndOfDxe, because EndOfDxe is last hook point that SMM code can call-out to get memory map information. A platform MUST finish SMM communication buffer allocation before EndOfDxe. If a DXE or OS driver need do communication after EndOfDxe, it can either allocate SMM communication buffer before EndOfDxe and save it, or consume EDKII_PI_SMM_COMMUNICATION_REGION_TABLE table to get general fixed comm buffer. This is designed to meet Microsoft WSMT table definition on FIXED_COMM_BUFFERS requirement. Cc: Liming Gao <liming.gao@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Jiewen Yao <jiewen.yao@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>