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Support for changing an enclave page's type enables an initialized enclave to be expanded with support for more threads by changing the type of a regular enclave page to that of a Thread Control Structure (TCS). Additionally, being able to change a TCS or regular enclave page's type to be trimmed (SGX_PAGE_TYPE_TRIM) initiates the removal of the page from the enclave. Test changing page type to TCS as well as page removal flows in two phases: In the first phase support for a new thread is dynamically added to an initialized enclave and in the second phase the pages associated with the new thread are removed from the enclave. As an additional sanity check after the second phase the page used as a TCS page during the first phase is added back as a regular page and ensured that it can be written to (which is not possible if it was a TCS page). Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/d05b48b00338683a94dcaef9f478540fc3d6d5f9.1652137848.git.reinette.chatre@intel.com