[RFC PATCH v2 13/26] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

Kai Huang
2021-01-18T03:29:38Z

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

The bare-metal kernel must intercept ECREATE to be able to impose policies
on guests. When it does this, the bare-metal kernel runs ECREATE against
the userspace mapping of the virtualized EPC.

Provide wrappers around __ecreate() and __einit() to hide the ugliness
of overloading the ENCLS return value to encode multiple error formats
in a single int. KVM will trap-and-execute ECREATE and EINIT as part
of SGX virtualization, and on an exception, KVM needs the trapnr so that
it can inject the correct fault into the guest.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
[Kai: Use sgx_update_lepubkeyhash() to update pubkey hash MSRs.]
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
v1->v2:

- Refined commit msg based on Dave's comment.
- Added comment to explain why to use __uaccess_xxx().
---
arch/x86/include/asm/sgx.h | 16 +++++++++
arch/x86/kernel/cpu/sgx/virt.c | 61 ++++++++++++++++++++++++++++++++++
2 files changed, 77 insertions(+)
create mode 100644 arch/x86/include/asm/sgx.h

diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
new file mode 100644
index 000000000000..0d643b985085
--- /dev/null
+++ b/arch/x86/include/asm/sgx.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SGX_H
+#define _ASM_X86_SGX_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_X86_SGX_VIRTUALIZATION
+struct sgx_pageinfo;
+
+int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
+ int *trapnr);
+int sgx_virt_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 1e8620f20651..97f02e5235ca 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -253,3 +253,64 @@ int __init sgx_virt_epc_init(void)

return misc_register(&sgx_virt_epc_dev);
}
+
+int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
+ int *trapnr)
+{
+ int ret;
+
+ /*
+ * @secs is userspace address, and it's not guaranteed @secs points at
+ * an actual EPC page. It's also possible to generate a kernel mapping
+ * to physical EPC page by resolving PFN but using __uaccess_xx() is
+ * simpler.
+ */
+ __uaccess_begin();
+ ret = __ecreate(pageinfo, (void *)secs);
+ __uaccess_end();
+
+ if (encls_faulted(ret)) {
+ *trapnr = ENCLS_TRAPNR(ret);
+ return -EFAULT;
+ }
+
+ /* ECREATE doesn't return an error code, it faults or succeeds. */
+ WARN_ON_ONCE(ret);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(sgx_virt_ecreate);
+
+static int __sgx_virt_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_virt_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_virt_einit(sigstruct, token, secs);
+ } else {
+ preempt_disable();
+
+ sgx_update_lepubkeyhash(lepubkeyhash);
+
+ ret = __sgx_virt_einit(sigstruct, token, secs);
+ preempt_enable();
+ }
+
+ if (encls_faulted(ret)) {
+ *trapnr = ENCLS_TRAPNR(ret);
+ return -EFAULT;
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(sgx_virt_einit);
--
2.29.2