Re: [PATCH REPOST v4 4/4] acpi/virt: suppress UART device & SPCR when guest has no serial hardware

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, May 28, 2025 at 06:53:38PM +0800, Li Chen wrote:
> 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.
> 
> And also explicitly add "-serial stdio" in bios-tables-test.c to allow
> serial device creation, otherwise DSDT assert would get failure because
> "-nodefaults" will not create uart device by default:
> 
> ```
> stderr:
> acpi-test: Warning! DSDT binary file mismatch. Actual [aml:/tmp/aml-BMOL72], Expected [aml:tests/data/acpi/aarch64/virt/DSDT].
> See source file tests/qtest/bios-tables-test.c for instructions on how to update expected files.
> acpi-test: Warning! DSDT mismatch. Actual [asl:/tmp/asl-RNOL72.dsl, aml:/tmp/aml-BMOL72], Expected [asl:/tmp/asl-ZVQL72.dsl, aml:tests/data/acpi/aarch64/virt/DS
> DT].
> ```
> 
> Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
> Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>


will need to be rebased updating loongarch too, now.


> ---
> 
> Notes:
>     Changes since v3: 1. Add Reviewed-by from Sunil V L <sunilvl@ventanamicro.com>
>                       2. Explicitly add "-serial stdio" to pass DSDT assert
> 
>  hw/arm/virt-acpi-build.c       | 15 +++++++++------
>  hw/riscv/virt-acpi-build.c     |  7 +++++--
>  include/system/system.h        |  2 ++
>  system/vl.c                    |  5 +++++
>  tests/qtest/bios-tables-test.c |  5 +++--
>  5 files changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index d77d16cbd3..c26aedb1b1 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
>  
> @@ -821,11 +822,13 @@ 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]);
> @@ -937,7 +940,7 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
>  
>      acpi_add_table(table_offsets, tables_blob);
>  
> -    if (ms->acpi_spcr_enabled) {
> +    if (ms->acpi_spcr_enabled && 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 ee1416d264..80bf3c3cec 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))
> @@ -474,7 +475,9 @@ 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);
> +

coding style violation

>      if (virt_is_iommu_sys_enabled(s)) {
>          acpi_dsdt_add_iommu_sys(scope, &memmap[VIRT_IOMMU_SYS], IOMMU_SYS_IRQ);
>      }
> @@ -895,7 +898,7 @@ static void virt_acpi_build(RISCVVirtState *s, AcpiBuildTables *tables)
>  
>      acpi_add_table(table_offsets, tables_blob);
>  
> -    if (ms->acpi_spcr_enabled) {
> +    if (ms->acpi_spcr_enabled && 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 fd402b8ff8..e340ee3a95 100644
> --- a/system/vl.c
> +++ b/system/vl.c
> @@ -1485,6 +1485,11 @@ Chardev *serial_hd(int i)
>      return NULL;
>  }
>  
> +bool serial_exist(void)
> +{
> +    return serial_hd(0) ? true : false;
> +}
> +

serial_exists


>  static bool parallel_parse(const char *devname, Error **errp)
>  {
>      static int index = 0;
> diff --git a/tests/qtest/bios-tables-test.c b/tests/qtest/bios-tables-test.c
> index 44de152a36..452566fa86 100644
> --- a/tests/qtest/bios-tables-test.c
> +++ b/tests/qtest/bios-tables-test.c
> @@ -824,10 +824,11 @@ static char *test_acpi_create_args(test_data *data, const char *params)
>          /*
>           * TODO: convert '-drive if=pflash' to new syntax (see e33763be7cd3)
>           * when arm/virt boad starts to support it.
> +         * NOTE: Explicitly add "-serial stdio" to enable uart in DSDT.
>           */
>          if (data->cd) {
>              args = g_strdup_printf("-machine %s%s %s -accel tcg "
> -                "-nodefaults -nographic "
> +                "-nodefaults -serial stdio -nographic "
>                  "-drive if=pflash,format=raw,file=%s,readonly=on "
>                  "-drive if=pflash,format=raw,file=%s,snapshot=on -cdrom %s %s",
>                  data->machine, data->machine_param ?: "",
> @@ -835,7 +836,7 @@ static char *test_acpi_create_args(test_data *data, const char *params)
>                  data->uefi_fl1, data->uefi_fl2, data->cd, params ? params : "");
>          } else {
>              args = g_strdup_printf("-machine %s%s %s -accel tcg "
> -                "-nodefaults -nographic "
> +                "-nodefaults -serial stdio -nographic "
>                  "-drive if=pflash,format=raw,file=%s,readonly=on "
>                  "-drive if=pflash,format=raw,file=%s,snapshot=on %s",
>                  data->machine, data->machine_param ?: "",




> -- 
> 2.49.0