HV: add simple parser for ACPI data table

Per ACPI spec, there are two fundamental types of ACPI tables:

Tables that contain AML code produced from the ACPI Source Language (ASL).
These include the DSDT, any SSDTs, and sometimes OEM-specific tables (OEMx).

Tables that contain simple data and no AML byte code. These types of tables
are known as ACPI Data Tables. They include tables such as the FADT, MADT,
ECDT, SRAT, etc. -essentially any table other than a DSDT or SSDT.

The second type of table, the ACPI Data Table, could be parsed here.

If Kconfig of CONSTANT_ACPI is set to yes, this parser is not needed.

Tracked-On: #1264

Signed-off-by: Victor Sun <victor.sun@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: jsun26intel

hypervisor/boot/acpi.c

@@ -34,6 +34,7 @@
 #define ACPI_SIG_RSDP             "RSD PTR " /* Root System Description Ptr */
 #define ACPI_OEM_ID_SIZE           6
 #define ACPI_SIG_MADT             "APIC" /* Multiple APIC Description Table */
+#define ACPI_SIG_FADT             "FACP" /* Fixed ACPI Description Table */
 #define ACPI_SIG_DMAR             "DMAR"
 #define RSDP_CHECKSUM_LENGTH       20
 #define ACPI_NAME_SIZE             4U
@@ -281,3 +282,86 @@ void *get_dmar_table(void)
 {
 	return get_acpi_tbl(ACPI_SIG_DMAR);
 }
+
+#ifndef CONFIG_CONSTANT_ACPI
+/* Per ACPI spec:
+ * There are two fundamental types of ACPI tables:
+ *
+ * Tables that contain AML code produced from the ACPI Source Language (ASL).
+ * These include the DSDT, any SSDTs, and sometimes OEM-specific tables (OEMx).
+ *
+ * Tables that contain simple data and no AML byte code. These types of tables
+ * are known as ACPI Data Tables. They include tables such as the FADT, MADT,
+ * ECDT, SRAT, etc. -essentially any table other than a DSDT or SSDT.
+ *
+ * The second type of table, the ACPI Data Table, could be parsed here.
+ *
+ * When ACRN go production, the platform ACPI data should be fixed. The
+ * Kconfig of CONSTANT_ACPI will be set to yes, then this code is not needed.
+ */
+
+#define ACPI_SIG_FACS		0x53434146U	/* "FACS" */
+
+/* FACP field offsets */
+#define OFFSET_FACS_ADDR	36U
+#define OFFSET_FACS_X_ADDR	132U
+
+/* FACS field offsets */
+#define OFFSET_FACS_SIGNATURE	0U
+#define OFFSET_FACS_LENGTH	4U
+#define OFFSET_WAKE_VECTOR_32	12U
+#define OFFSET_WAKE_VECTOR_64	24U
+
+/* get a dword value from given table and its offset */
+static inline uint32_t get_acpi_dt_dword(uint8_t *dt_addr, uint32_t dt_offset)
+{
+	return *(uint32_t *)(dt_addr + dt_offset);
+}
+
+/* get a qword value from given table and its offset */
+static inline uint64_t get_acpi_dt_qword(uint8_t *dt_addr, uint32_t dt_offset)
+{
+	return *(uint64_t *)(dt_addr + dt_offset);
+}
+
+static void *get_facs_table(void)
+{
+	uint8_t *facp_addr, *facs_addr, *facs_x_addr;
+	uint32_t signature, length;
+
+	facp_addr = (uint8_t *)get_acpi_tbl(ACPI_SIG_FADT);
+
+	if (facp_addr == NULL) {
+		return NULL;
+	}
+
+	facs_addr = (uint8_t *)(uint64_t)get_acpi_dt_dword(facp_addr,
+						OFFSET_FACS_ADDR);
+
+	facs_x_addr = (uint8_t *)get_acpi_dt_qword(facp_addr,
+						OFFSET_FACS_X_ADDR);
+
+	if (facs_x_addr != NULL) {
+		facs_addr = facs_x_addr;
+	}
+
+	if (facs_addr == NULL) {
+		return NULL;
+	}
+
+	signature = get_acpi_dt_dword(facs_addr, OFFSET_FACS_SIGNATURE);
+
+	if (signature != ACPI_SIG_FACS) {
+		return NULL;
+	}
+
+	length = get_acpi_dt_dword(facs_addr, OFFSET_FACS_LENGTH);
+
+	if (length < 64U) {
+		return NULL;
+	}
+
+	return facs_addr;
+}
+
+#endif