[RFC PATCH v3 05/27] x86/sgx: Add SGX_CHILD_PRESENT hardware error code

[Kai Huang <kai.huang@intel.com>]

From: Sean Christopherson <sean.j.christopherson@intel.com>

SGX virtualization requires to allocate "raw" EPC and use it as "virtual
EPC" for SGX guest.  Unlike EPC used by SGX driver, virtual EPC doesn't
track how EPC pages are used in VM, e.g. (de)construction of enclaves,
so it cannot guarantee EREMOVE success, e.g. it doesn't have a priori
knowledge of which pages are SECS with non-zero child counts.

Add SGX_CHILD_PRESENT for use by SGX virtualization to assert EREMOVE
failures are expected, but only due to SGX_CHILD_PRESENT.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
v2->v3:

 - Changed from 'Enclave has child' to 'SECS has child', per Jarkko.

---
 arch/x86/kernel/cpu/sgx/arch.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/arch.h b/arch/x86/kernel/cpu/sgx/arch.h
index dd7602c44c72..abf99bb71fdc 100644
--- a/arch/x86/kernel/cpu/sgx/arch.h
+++ b/arch/x86/kernel/cpu/sgx/arch.h
@@ -26,12 +26,14 @@
  * enum sgx_return_code - The return code type for ENCLS, ENCLU and ENCLV
  * %SGX_NOT_TRACKED:		Previous ETRACK's shootdown sequence has not
  *				been completed yet.
+ * %SGX_CHILD_PRESENT		SECS has child pages present in the EPC.
  * %SGX_INVALID_EINITTOKEN:	EINITTOKEN is invalid and enclave signer's
  *				public key does not match IA32_SGXLEPUBKEYHASH.
  * %SGX_UNMASKED_EVENT:		An unmasked event, e.g. INTR, was received
  */
 enum sgx_return_code {
 	SGX_NOT_TRACKED			= 11,
+	SGX_CHILD_PRESENT		= 13,
 	SGX_INVALID_EINITTOKEN		= 16,
 	SGX_UNMASKED_EVENT		= 128,
 };
-- 
2.29.2