[PATCH V3 4/4] acpi/virt: suppress UART device & SPCR when guest has no serial hardware

[Li Chen <me@linux.beauty>]

From: Li Chen <chenl311@chinatelecom.cn>

The virt machines always instantiate a PL011/16550 at UART0 and
describe it in ACPI (DSDT device node plus optional SPCR table).  When
the command line contains “-serial none” there is no backend attached to
that UART, yet the guest still discovers it via ACPI and may try to use
it as a console, causing unexpected results.

Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
---

 hw/arm/virt-acpi-build.c   | 15 +++++++++------
 hw/riscv/virt-acpi-build.c |  6 ++++--
 include/system/system.h    |  2 ++
 system/vl.c                |  5 +++++
 4 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index f25c3b26ce..8a1cde4b44 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -59,6 +59,7 @@
 #include "hw/acpi/viot.h"
 #include "hw/virtio/virtio-acpi.h"
 #include "target/arm/multiprocessing.h"
+#include "system/system.h"
 
 #define ARM_SPI_BASE 32
 
@@ -825,11 +826,13 @@ 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), 0);
-    if (vms->second_ns_uart_present) {
-        acpi_dsdt_add_uart(scope, &memmap[VIRT_UART1],
-                           (irqmap[VIRT_UART1] + ARM_SPI_BASE), 1);
+    if (serial_exist()) {
+        acpi_dsdt_add_uart(scope, &memmap[VIRT_UART0],
+                           (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]);
@@ -941,7 +944,7 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
 
     acpi_add_table(table_offsets, tables_blob);
 
-    if (ms->enable_spcr) {
+    if (ms->enable_spcr && serial_exist()) {
         spcr_setup(tables_blob, tables->linker, vms);
     }
 
diff --git a/hw/riscv/virt-acpi-build.c b/hw/riscv/virt-acpi-build.c
index 7f6d221c63..4e0f695a16 100644
--- a/hw/riscv/virt-acpi-build.c
+++ b/hw/riscv/virt-acpi-build.c
@@ -39,6 +39,7 @@
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "system/reset.h"
+#include "system/system.h"
 
 #define ACPI_BUILD_TABLE_SIZE             0x20000
 #define ACPI_BUILD_INTC_ID(socket, index) ((socket << 24) | (index))
@@ -449,7 +450,8 @@ static void build_dsdt(GArray *table_data,
                                  memmap[VIRT_APLIC_S].size, "RSCV0002");
     }
 
-    acpi_dsdt_add_uart(scope, &memmap[VIRT_UART0], UART0_IRQ);
+    if (serial_exist())
+        acpi_dsdt_add_uart(scope, &memmap[VIRT_UART0], UART0_IRQ);
 
     if (socket_count == 1) {
         virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
@@ -681,7 +683,7 @@ static void virt_acpi_build(RISCVVirtState *s, AcpiBuildTables *tables)
 
     acpi_add_table(table_offsets, tables_blob);
 
-    if (ms->enable_spcr) {
+    if (ms->enable_spcr && serial_exist()) {
         spcr_setup(tables_blob, tables->linker, s);
     }
 
diff --git a/include/system/system.h b/include/system/system.h
index a7effe7dfd..ca1af38432 100644
--- a/include/system/system.h
+++ b/include/system/system.h
@@ -75,6 +75,8 @@ extern unsigned int nb_prom_envs;
 /* Return the Chardev for serial port i, or NULL if none */
 Chardev *serial_hd(int i);
 
+bool serial_exist(void);
+
 /* parallel ports */
 
 #define MAX_PARALLEL_PORTS 3
diff --git a/system/vl.c b/system/vl.c
index 520956f4a1..7e219df7bf 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -1484,6 +1484,11 @@ Chardev *serial_hd(int i)
     return NULL;
 }
 
+bool serial_exist(void)
+{
+    return serial_hd(0) ? true : false;
+}
+
 static bool parallel_parse(const char *devname, Error **errp)
 {
     static int index = 0;
-- 
2.49.0