Documentation/x86: Document SGX kernel architecture

mainline inclusion
from mainline-v5.11-rc1
commit 3fa97bf0
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SIGI


CVE: NA

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Document the Intel SGX kernel architecture. The fine-grained architecture
details can be looked up from Intel SDM Volume 3D.

Intel-SIG: commit 3fa97bf0 Documentation/x86: Document SGX kernel architecture
Backport for SGX Foundations support

Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jethro Beekman <jethro@fortanix.com>
Cc: linux-doc@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112220135.165028-24-jarkko@kernel.org


Signed-off-by: Fan Du <fan.du@intel.com> #openEuler_contributor
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Bamvor Zhang <bamvor.zhang@suse.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>