[RFC PATCH 14/21] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

[Sean Christopherson <sean.j.christopherson@intel.com>]

Provide wrappers around __ecreate() and __einit() to export their
functionality for use by KVM without having to export a large amount of
SGX boilerplate code.  Intermediate helpers also shelter KVM from the
ugliness of overloading the ENCLS return value to encode multiple error
formats in a single int.

KVM will use the helpers to trap-and-execute ECREATE and EINIT as part
its SGX virtualization.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/Kconfig               |  3 ++
 arch/x86/include/asm/sgx.h     | 15 ++++++++++
 arch/x86/kernel/cpu/sgx/virt.c | 55 ++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 arch/x86/include/asm/sgx.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1bdb9f85928..8bbc6a30588d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1969,6 +1969,9 @@ config INTEL_SGX_VIRTUALIZATION
 	  "raw" EPC for the purpose of exposing EPC to a KVM guest, i.e. a
 	  virtual machine, via a device node (/dev/sgx/virt_epc by default).
 
+	  SGX virtualization also adds helpers that are used by KVM to trap
+	  and execute certain ENCLS instructions on behalf of a KVM guest.
+
 	  If unsure, say N.
 
 config EFI
diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
new file mode 100644
index 000000000000..f0f0176b8e2f
--- /dev/null
+++ b/arch/x86/include/asm/sgx.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SGX_H
+#define _ASM_X86_SGX_H
+
+#include <linux/types.h>
+
+struct sgx_pageinfo;
+
+#if IS_ENABLED(CONFIG_KVM_INTEL)
+int sgx_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, int *trapnr);
+int sgx_einit(void __user *sigstruct, void __user *token,
+	      void __user *secs, u64 *lepubkeyhash, int *trapnr);
+#endif
+
+#endif /* _ASM_X86_SGX_H */
diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
index 79ee5917a4fc..9e5bf4450bf7 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -251,3 +251,58 @@ int __init sgx_virt_epc_init(void)
 
 	return ret;
 }
+
+#if IS_ENABLED(CONFIG_KVM_INTEL)
+int sgx_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, int *trapnr)
+{
+	int ret;
+
+	__uaccess_begin();
+	ret = __ecreate(pageinfo, (void *)secs);
+	__uaccess_end();
+
+	if (encls_faulted(ret)) {
+		*trapnr = ENCLS_TRAPNR(ret);
+		return -EFAULT;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(sgx_ecreate);
+
+static int __sgx_einit(void __user *sigstruct, void __user *token,
+		       void __user *secs)
+{
+	int ret;
+
+	__uaccess_begin();
+	ret =  __einit((void *)sigstruct, (void *)token, (void *)secs);
+	__uaccess_end();
+	return ret;
+}
+
+int sgx_einit(void __user *sigstruct, void __user *token,
+	      void __user *secs, u64 *lepubkeyhash, int *trapnr)
+{
+	int ret;
+
+	if (!boot_cpu_has(X86_FEATURE_SGX_LC)) {
+		ret = __sgx_einit(sigstruct, token, secs);
+	} else {
+		preempt_disable();
+		sgx_update_lepubkeyhash_msrs(lepubkeyhash, false);
+		ret = __sgx_einit(sigstruct, token, secs);
+		if (ret == SGX_INVALID_EINITTOKEN) {
+			sgx_update_lepubkeyhash_msrs(lepubkeyhash, true);
+			ret = __sgx_einit(sigstruct, token, secs);
+		}
+		preempt_enable();
+	}
+
+	if (encls_faulted(ret)) {
+		*trapnr = ENCLS_TRAPNR(ret);
+		return -EFAULT;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(sgx_einit);
+#endif
-- 
2.22.0