acpi: add mcfg table for mmconfig

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/src/acpi.c b/src/acpi.c
index 72c8fe8..6267d7b 100644
--- a/src/acpi.c
+++ b/src/acpi.c
@@ -764,6 +764,27 @@
     return srat;
 }
 
+static void *
+build_mcfg_q35(void)
+{
+    struct acpi_table_mcfg *mcfg;
+
+    int len = sizeof(*mcfg) + 1 * sizeof(mcfg->allocation[0]);
+    mcfg = malloc_high(len);
+    if (!mcfg) {
+        warn_noalloc();
+        return NULL;
+    }
+    memset(mcfg, 0, len);
+    mcfg->allocation[0].address = Q35_HOST_BRIDGE_PCIEXBAR_ADDR;
+    mcfg->allocation[0].pci_segment = Q35_HOST_PCIE_PCI_SEGMENT;
+    mcfg->allocation[0].start_bus_number = Q35_HOST_PCIE_START_BUS_NUMBER;
+    mcfg->allocation[0].end_bus_number = Q35_HOST_PCIE_END_BUS_NUMBER;
+
+    build_header((void *)mcfg, MCFG_SIGNATURE, len, 1);
+    return mcfg;
+}
+
 static const struct pci_device_id acpi_find_tbl[] = {
     /* PIIX4 Power Management device. */
     PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3, NULL),
@@ -804,6 +825,8 @@
     ACPI_INIT_TABLE(build_madt());
     ACPI_INIT_TABLE(build_hpet());
     ACPI_INIT_TABLE(build_srat());
+    if (pci->device == PCI_DEVICE_ID_INTEL_ICH9_LPC)
+        ACPI_INIT_TABLE(build_mcfg_q35());
 
     u16 i, external_tables = qemu_cfg_acpi_additional_tables();
 
diff --git a/src/acpi.h b/src/acpi.h
index cb21561..715d19d 100644
--- a/src/acpi.h
+++ b/src/acpi.h
@@ -107,4 +107,21 @@
     u64 p1l;  /* pci window 1 (above 4g) - length */
 } PACKED;
 
+/* PCI fw r3.0 MCFG table. */
+/* Subtable */
+struct acpi_mcfg_allocation {
+    u64 address;                /* Base address, processor-relative */
+    u16 pci_segment;            /* PCI segment group number */
+    u8 start_bus_number;       /* Starting PCI Bus number */
+    u8 end_bus_number;         /* Final PCI Bus number */
+    u32 reserved;
+} PACKED;
+
+#define MCFG_SIGNATURE 0x4746434d       // MCFG
+struct acpi_table_mcfg {
+    ACPI_TABLE_HEADER_DEF;
+    u8 reserved[8];
+    struct acpi_mcfg_allocation allocation[0];
+} PACKED;
+
 #endif // acpi.h