x86/boot/compressed/64: Setup a GHCB-based VC Exception handler

Install an exception handler for #VC exception that uses a GHCB. Also
add the infrastructure for handling different exit-codes by decoding
the instruction that caused the exception and error handling.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-24-joro@8bytes.org

1 files changed, 154 insertions, 0 deletions

diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index 0bea32341afa..7ac6e6b0ae57 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -9,6 +9,118 @@
  * and is included directly into both code-bases.
  */
 
+static void sev_es_terminate(unsigned int reason)
+{
+	u64 val = GHCB_SEV_TERMINATE;
+
+	/*
+	 * Tell the hypervisor what went wrong - only reason-set 0 is
+	 * currently supported.
+	 */
+	val |= GHCB_SEV_TERMINATE_REASON(0, reason);
+
+	/* Request Guest Termination from Hypvervisor */
+	sev_es_wr_ghcb_msr(val);
+	VMGEXIT();
+
+	while (true)
+		asm volatile("hlt\n" : : : "memory");
+}
+
+static bool sev_es_negotiate_protocol(void)
+{
+	u64 val;
+
+	/* Do the GHCB protocol version negotiation */
+	sev_es_wr_ghcb_msr(GHCB_SEV_INFO_REQ);
+	VMGEXIT();
+	val = sev_es_rd_ghcb_msr();
+
+	if (GHCB_INFO(val) != GHCB_SEV_INFO)
+		return false;
+
+	if (GHCB_PROTO_MAX(val) < GHCB_PROTO_OUR ||
+	    GHCB_PROTO_MIN(val) > GHCB_PROTO_OUR)
+		return false;
+
+	return true;
+}
+
+static void vc_ghcb_invalidate(struct ghcb *ghcb)
+{
+	memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
+}
+
+static bool vc_decoding_needed(unsigned long exit_code)
+{
+	/* Exceptions don't require to decode the instruction */
+	return !(exit_code >= SVM_EXIT_EXCP_BASE &&
+		 exit_code <= SVM_EXIT_LAST_EXCP);
+}
+
+static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt,
+				      struct pt_regs *regs,
+				      unsigned long exit_code)
+{
+	enum es_result ret = ES_OK;
+
+	memset(ctxt, 0, sizeof(*ctxt));
+	ctxt->regs = regs;
+
+	if (vc_decoding_needed(exit_code))
+		ret = vc_decode_insn(ctxt);
+
+	return ret;
+}
+
+static void vc_finish_insn(struct es_em_ctxt *ctxt)
+{
+	ctxt->regs->ip += ctxt->insn.length;
+}
+
+static 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)
+{
+	enum es_result ret;
+
+	/* Fill in protocol and format specifiers */
+	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
+	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();
+
+	if ((ghcb->save.sw_exit_info_1 & 0xffffffff) == 1) {
+		u64 info = ghcb->save.sw_exit_info_2;
+		unsigned long v;
+
+		info = ghcb->save.sw_exit_info_2;
+		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;
+			ret = ES_EXCEPTION;
+		} else {
+			ret = ES_VMM_ERROR;
+		}
+	} else {
+		ret = ES_OK;
+	}
+
+	return ret;
+}
+
 /*
  * Boot VC Handler - This is the first VC handler during boot, there is no GHCB
  * page yet, so it only supports the MSR based communication with the
@@ -64,3 +176,45 @@ fail:
 	while (true)
 		asm volatile("hlt\n");
 }
+
+static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
+					  void *src, char *buf,
+					  unsigned int data_size,
+					  unsigned int count,
+					  bool backwards)
+{
+	int i, b = backwards ? -1 : 1;
+	enum es_result ret = ES_OK;
+
+	for (i = 0; i < count; i++) {
+		void *s = src + (i * data_size * b);
+		char *d = buf + (i * data_size);
+
+		ret = vc_read_mem(ctxt, s, d, data_size);
+		if (ret != ES_OK)
+			break;
+	}
+
+	return ret;
+}
+
+static enum es_result vc_insn_string_write(struct es_em_ctxt *ctxt,
+					   void *dst, char *buf,
+					   unsigned int data_size,
+					   unsigned int count,
+					   bool backwards)
+{
+	int i, s = backwards ? -1 : 1;
+	enum es_result ret = ES_OK;
+
+	for (i = 0; i < count; i++) {
+		void *d = dst + (i * data_size * s);
+		char *b = buf + (i * data_size);
+
+		ret = vc_write_mem(ctxt, d, b, data_size);
+		if (ret != ES_OK)
+			break;
+	}
+
+	return ret;
+}