x86/sgx: Add wrapper for SGX2 EMODT function

mainline inclusion
from mainline-6.0-rc1
commit 09b38d0b
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5USAM


CVE: NA

Intel-SIG: commit 09b38d0b x86/sgx: Add wrapper for SGX2 EMODT
function.
Backport for SGX EDMM support.

--------------------------------

Add a wrapper for the EMODT ENCLS leaf function used to
change the type of an enclave page as maintained in the
SGX hardware's Enclave Page Cache Map (EPCM).

EMODT:
1) Updates the EPCM page type of the enclave page.
2) Sets the MODIFIED bit in the EPCM entry of the enclave page.
   This bit is reset by the enclave by invoking ENCLU leaf
   function EACCEPT or EACCEPTCOPY.

Access from within the enclave to the enclave page is not possible
while the MODIFIED bit is set.

After changing the enclave page type by issuing EMODT the kernel
needs to collaborate with the hardware to ensure that no logical
processor continues to hold a reference to the changed page. This
is required to ensure no required security checks are circumvented
and is required for the enclave's EACCEPT/EACCEPTCOPY to succeed.
Ensuring that no references to the changed page remain is
accomplished with the ETRACK flow.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/dba63a8c0db1d510b940beee1ba2a8207efeb1f1.1652137848.git.reinette.chatre@intel.com


Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>