x86/sgx: Add helper to update SGX_LEPUBKEYHASHn MSRs

Add a helper to update SGX_LEPUBKEYHASHn MSRs.  SGX virtualization also
needs to update those MSRs based on guest's "virtual" SGX_LEPUBKEYHASHn
before EINIT from guest.
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/dfb7cd39d4dd62ea27703b64afdd8bccb579f623.1616136308.git.kai.huang@intel.com

arch/x86/kernel/cpu/sgx/ioctl.c

@@ -495,7 +495,7 @@ static int sgx_encl_init(struct sgx_encl *encl, struct sgx_sigstruct *sigstruct,
 			 void *token)
 {
 	u64 mrsigner[4];
-	int i, j, k;
+	int i, j;
 	void *addr;
 	int ret;
 
@@ -544,8 +544,7 @@ static int sgx_encl_init(struct sgx_encl *encl, struct sgx_sigstruct *sigstruct,
 
 			preempt_disable();
 
-			for (k = 0; k < 4; k++)
-				wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + k, mrsigner[k]);
+			sgx_update_lepubkeyhash(mrsigner);
 
 			ret = __einit(sigstruct, token, addr);
 

arch/x86/kernel/cpu/sgx/main.c

@@ -727,6 +727,22 @@ static bool __init sgx_page_cache_init(void)
 	return true;
 }
 
+/*
+ * Update the SGX_LEPUBKEYHASH MSRs to the values specified by caller.
+ * Bare-metal driver requires to update them to hash of enclave's signer
+ * before EINIT. KVM needs to update them to guest's virtual MSR values
+ * before doing EINIT from guest.
+ */
+void sgx_update_lepubkeyhash(u64 *lepubkeyhash)
+{
+	int i;
+
+	WARN_ON_ONCE(preemptible());
+
+	for (i = 0; i < 4; i++)
+		wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + i, lepubkeyhash[i]);
+}
+
 static int __init sgx_init(void)
 {
 	int ret;

arch/x86/kernel/cpu/sgx/sgx.h

@@ -93,4 +93,6 @@ static inline int __init sgx_vepc_init(void)
 }
 #endif
 
+void sgx_update_lepubkeyhash(u64 *lepubkeyhash);
+
 #endif /* _X86_SGX_H */