3 files changed, 172 insertions, 0 deletions

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 14ef5908fb27..2a28d14425d4 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -101,6 +101,15 @@ DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
 u8 snp_vmpl __ro_after_init;
 EXPORT_SYMBOL_GPL(snp_vmpl);
 
+/* For early boot hypervisor communication in SEV-ES enabled guests */
+static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
+
+/*
+ * Needs to be in the .data section because we need it NULL before bss is
+ * cleared
+ */
+struct ghcb *boot_ghcb __section(".data");
+
 static u64 __init get_snp_jump_table_addr(void)
 {
 	struct snp_secrets_page *secrets;
@@ -154,6 +163,73 @@ static u64 __init get_jump_table_addr(void)
 	return ret;
 }
 
+static int svsm_perform_ghcb_protocol(struct ghcb *ghcb, struct svsm_call *call)
+{
+	struct es_em_ctxt ctxt;
+	u8 pending = 0;
+
+	vc_ghcb_invalidate(ghcb);
+
+	/*
+	 * Fill in protocol and format specifiers. This can be called very early
+	 * in the boot, so use rip-relative references as needed.
+	 */
+	ghcb->protocol_version = ghcb_version;
+	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
+
+	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_SNP_RUN_VMPL);
+	ghcb_set_sw_exit_info_1(ghcb, 0);
+	ghcb_set_sw_exit_info_2(ghcb, 0);
+
+	sev_es_wr_ghcb_msr(__pa(ghcb));
+
+	svsm_issue_call(call, &pending);
+
+	if (pending)
+		return -EINVAL;
+
+	switch (verify_exception_info(ghcb, &ctxt)) {
+	case ES_OK:
+		break;
+	case ES_EXCEPTION:
+		vc_forward_exception(&ctxt);
+		fallthrough;
+	default:
+		return -EINVAL;
+	}
+
+	return svsm_process_result_codes(call);
+}
+
+static int svsm_perform_call_protocol(struct svsm_call *call)
+{
+	struct ghcb_state state;
+	unsigned long flags;
+	struct ghcb *ghcb;
+	int ret;
+
+	flags = native_local_irq_save();
+
+	if (sev_cfg.ghcbs_initialized)
+		ghcb = __sev_get_ghcb(&state);
+	else if (boot_ghcb)
+		ghcb = boot_ghcb;
+	else
+		ghcb = NULL;
+
+	do {
+		ret = ghcb ? svsm_perform_ghcb_protocol(ghcb, call)
+			   : svsm_perform_msr_protocol(call);
+	} while (ret == -EAGAIN);
+
+	if (sev_cfg.ghcbs_initialized)
+		__sev_put_ghcb(&state);
+
+	native_local_irq_restore(flags);
+
+	return ret;
+}
+
 static inline void __pval_terminate(u64 pfn, bool action, unsigned int page_size,
 				    int ret, u64 svsm_ret)
 {
diff --git a/arch/x86/coco/sev/vc-handle.c b/arch/x86/coco/sev/vc-handle.c
index c3b4acbde0d8..357389456296 100644
--- a/arch/x86/coco/sev/vc-handle.c
+++ b/arch/x86/coco/sev/vc-handle.c
@@ -351,6 +351,8 @@ fault:
 }
 
 #define sev_printk(fmt, ...)		printk(fmt, ##__VA_ARGS__)
+#define error(v)
+#define has_cpuflag(f)			boot_cpu_has(f)
 
 #include "vc-shared.c"
 
diff --git a/arch/x86/coco/sev/vc-shared.c b/arch/x86/coco/sev/vc-shared.c
index b4688f69102e..9b01c9ad81be 100644
--- a/arch/x86/coco/sev/vc-shared.c
+++ b/arch/x86/coco/sev/vc-shared.c
@@ -409,6 +409,53 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	return ret;
 }
 
+enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
+{
+	u32 ret;
+
+	ret = ghcb->save.sw_exit_info_1 & GENMASK_ULL(31, 0);
+	if (!ret)
+		return ES_OK;
+
+	if (ret == 1) {
+		u64 info = ghcb->save.sw_exit_info_2;
+		unsigned long v = info & SVM_EVTINJ_VEC_MASK;
+
+		/* Check if exception information from hypervisor is sane. */
+		if ((info & SVM_EVTINJ_VALID) &&
+		    ((v == X86_TRAP_GP) || (v == X86_TRAP_UD)) &&
+		    ((info & SVM_EVTINJ_TYPE_MASK) == SVM_EVTINJ_TYPE_EXEPT)) {
+			ctxt->fi.vector = v;
+
+			if (info & SVM_EVTINJ_VALID_ERR)
+				ctxt->fi.error_code = info >> 32;
+
+			return ES_EXCEPTION;
+		}
+	}
+
+	return ES_VMM_ERROR;
+}
+
+enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
+				   struct es_em_ctxt *ctxt,
+				   u64 exit_code, u64 exit_info_1,
+				   u64 exit_info_2)
+{
+	/* Fill in protocol and format specifiers */
+	ghcb->protocol_version = ghcb_version;
+	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
+
+	ghcb_set_sw_exit_code(ghcb, exit_code);
+	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
+	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
+
+	sev_es_wr_ghcb_msr(__pa(ghcb));
+	VMGEXIT();
+
+	return verify_exception_info(ghcb, ctxt);
+}
+
 static int __sev_cpuid_hv_ghcb(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
 {
 	u32 cr4 = native_read_cr4();
@@ -549,3 +596,50 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
 
 	return ES_OK;
 }
+
+void snp_register_ghcb_early(unsigned long paddr)
+{
+	unsigned long pfn = paddr >> PAGE_SHIFT;
+	u64 val;
+
+	sev_es_wr_ghcb_msr(GHCB_MSR_REG_GPA_REQ_VAL(pfn));
+	VMGEXIT();
+
+	val = sev_es_rd_ghcb_msr();
+
+	/* If the response GPA is not ours then abort the guest */
+	if ((GHCB_RESP_CODE(val) != GHCB_MSR_REG_GPA_RESP) ||
+	    (GHCB_MSR_REG_GPA_RESP_VAL(val) != pfn))
+		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
+}
+
+bool __init sev_es_check_cpu_features(void)
+{
+	if (!has_cpuflag(X86_FEATURE_RDRAND)) {
+		error("RDRAND instruction not supported - no trusted source of randomness available\n");
+		return false;
+	}
+
+	return true;
+}
+
+bool sev_es_negotiate_protocol(void)
+{
+	u64 val;
+
+	/* Do the GHCB protocol version negotiation */
+	sev_es_wr_ghcb_msr(GHCB_MSR_SEV_INFO_REQ);
+	VMGEXIT();
+	val = sev_es_rd_ghcb_msr();
+
+	if (GHCB_MSR_INFO(val) != GHCB_MSR_SEV_INFO_RESP)
+		return false;
+
+	if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTOCOL_MIN ||
+	    GHCB_MSR_PROTO_MIN(val) > GHCB_PROTOCOL_MAX)
+		return false;
+
+	ghcb_version = min_t(size_t, GHCB_MSR_PROTO_MAX(val), GHCB_PROTOCOL_MAX);
+
+	return true;
+}