2 files changed, 43 insertions, 7 deletions
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index eb5796e309..b2366f24f9 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -79,11 +79,11 @@ static void acpi_dsdt_add_cpus(Aml *scope, VirtMachineState *vms)
 }
 
 static void acpi_dsdt_add_uart(Aml *scope, const MemMapEntry *uart_memmap,
-                                           uint32_t uart_irq)
+                               uint32_t uart_irq, int uartidx)
 {
-    Aml *dev = aml_device("COM0");
+    Aml *dev = aml_device("COM%d", uartidx);
     aml_append(dev, aml_name_decl("_HID", aml_string("ARMH0011")));
-    aml_append(dev, aml_name_decl("_UID", aml_int(0)));
+    aml_append(dev, aml_name_decl("_UID", aml_int(uartidx)));
 
     Aml *crs = aml_resource_template();
     aml_append(crs, aml_memory32_fixed(uart_memmap->base,
@@ -817,7 +817,11 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
     scope = aml_scope("\\_SB");
     acpi_dsdt_add_cpus(scope, vms);
     acpi_dsdt_add_uart(scope, &memmap[VIRT_UART0],
-                       (irqmap[VIRT_UART0] + ARM_SPI_BASE));
+                       (irqmap[VIRT_UART0] + ARM_SPI_BASE), 0);
+    if (vms->second_ns_uart_present) {
+        acpi_dsdt_add_uart(scope, &memmap[VIRT_UART1],
+                           (irqmap[VIRT_UART1] + ARM_SPI_BASE), 1);
+    }
     if (vmc->acpi_expose_flash) {
         acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
     }
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index ffb4983885..8555615256 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -906,7 +906,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion *mem)
 }
 
 static void create_uart(const VirtMachineState *vms, int uart,
-                        MemoryRegion *mem, Chardev *chr)
+                        MemoryRegion *mem, Chardev *chr, bool secure)
 {
     char *nodename;
     hwaddr base = vms->memmap[uart].base;
@@ -944,6 +944,8 @@ static void create_uart(const VirtMachineState *vms, int uart,
         qemu_fdt_setprop_string(ms->fdt, "/aliases", "serial0", nodename);
     } else {
         qemu_fdt_setprop_string(ms->fdt, "/aliases", "serial1", nodename);
+    }
+    if (secure) {
         /* Mark as not usable by the normal world */
         qemu_fdt_setprop_string(ms->fdt, nodename, "status", "disabled");
         qemu_fdt_setprop_string(ms->fdt, nodename, "secure-status", "okay");
@@ -2317,11 +2319,41 @@ static void machvirt_init(MachineState *machine)
 
     fdt_add_pmu_nodes(vms);
 
-    create_uart(vms, VIRT_UART0, sysmem, serial_hd(0));
+    /*
+     * The first UART always exists. If the security extensions are
+     * enabled, the second UART also always exists. Otherwise, it only exists
+     * if a backend is configured explicitly via '-serial <backend>'.
+     * This avoids potentially breaking existing user setups that expect
+     * only one NonSecure UART to be present (for instance, older EDK2
+     * binaries).
+     *
+     * The nodes end up in the DTB in reverse order of creation, so we must
+     * create UART0 last to ensure it appears as the first node in the DTB,
+     * for compatibility with guest software that just iterates through the
+     * DTB to find the first UART, as older versions of EDK2 do.
+     * DTB readers that follow the spec, as Linux does, should honour the
+     * aliases node information and /chosen/stdout-path regardless of
+     * the order that nodes appear in the DTB.
+     *
+     * For similar back-compatibility reasons, if UART1 is the secure UART
+     * we create it second (and so it appears first in the DTB), because
+     * that's what QEMU has always done.
+     */
+    if (!vms->secure) {
+        Chardev *serial1 = serial_hd(1);
+
+        if (serial1) {
+            vms->second_ns_uart_present = true;
+            create_uart(vms, VIRT_UART1, sysmem, serial1, false);
+        }
+    }
+    create_uart(vms, VIRT_UART0, sysmem, serial_hd(0), false);
+    if (vms->secure) {
+        create_uart(vms, VIRT_UART1, secure_sysmem, serial_hd(1), true);
+    }
 
     if (vms->secure) {
         create_secure_ram(vms, secure_sysmem, secure_tag_sysmem);
-        create_uart(vms, VIRT_UART1, secure_sysmem, serial_hd(1));
     }
 
     if (tag_sysmem) {