[RFC PATCH v3 14/27] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

From: Kai Huang <kai.huang@intel.com>
To: linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org
Cc: seanjc@google.com, jarkko@kernel.org, luto@kernel.org,
	dave.hansen@intel.com, haitao.huang@intel.com,
	pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de,
	mingo@redhat.com, hpa@zytor.com, Kai Huang <kai.huang@intel.com>
Subject: [RFC PATCH v3 14/27] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM
Date: Tue, 26 Jan 2021 22:31:06 +1300	[thread overview]
Message-ID: <e807033e3d56ede1177d7a1af34477678bfbfff9.1611634586.git.kai.huang@intel.com> (raw)
In-Reply-To: <cover.1611634586.git.kai.huang@intel.com>

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>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
v2->v3:

 - Added kdoc for sgx_virt_ecreate() and sgx_virt_einit(), per Jarkko.
 - Changed to use CONFIG_X86_SGX_KVM.

---
 arch/x86/include/asm/sgx.h     | 16 ++++++
 arch/x86/kernel/cpu/sgx/virt.c | 93 ++++++++++++++++++++++++++++++++++
 2 files changed, 109 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..8a3ea3e1efbe
--- /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_KVM
+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 e1ad7856d878..0f5b0e4e33dd 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -252,3 +252,96 @@ int __init sgx_vepc_init(void)
 
 	return misc_register(&sgx_vepc_dev);
 }
+
+/**
+ * sgx_virt_ecreate() - Run ECREATE on behalf of guest
+ * @pageinfo:	Pointer to PAGEINFO structure
+ * @secs:	Userspace pointer to SECS page
+ * @trapnr:	trap number injected to guest in case of ECREATE error
+ *
+ * Run ECREATE on behalf of guest after KVM traps ECREATE for the purpose
+ * of enforcing policies of guest's enclaves, and return the trap number
+ * which should be injected to guest in case of any ECREATE error.
+ *
+ * Return:
+ * - 0: 	ECREATE was successful.
+ * - -EFAULT:	ECREATE returned error.
+ */
+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;
+}
+
+/**
+ * sgx_virt_ecreate() - Run EINIT on behalf of guest
+ * @sigstruct:		Userspace pointer to SIGSTRUCT structure
+ * @token:		Userspace pointer to EINITTOKEN structure
+ * @secs:		Userspace pointer to SECS page
+ * @lepubkeyhash:	Pointer to guest's *virtual* SGX_LEPUBKEYHASH MSR
+ * 			values
+ * @trapnr:		trap number injected to guest in case of EINIT error
+ *
+ * Run EINIT on behalf of guest after KVM traps EINIT. If SGX_LC is available
+ * in host, bare-metal driver may rewrite the hardware values, therefore KVM
+ * needs to update hardware values to guest's virtual MSR values in order to
+ * ensure EINIT is executed with expected hardware values.
+ *
+ * Return:
+ * - 0: 	EINIT was successful.
+ * - -EFAULT:	EINIT returned error.
+ */
+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

