Re: [PATCH V2 1/3] acpi: Add machine option to disable SPCR table

[Li Chen]

Hi Gavin,

 ---- On Wed, 23 Apr 2025 08:11:24 +0800  Gavin Shan <gshan@redhat.com> wrote 
--- 
 > On 4/22/25 10:05 PM, Li Chen wrote:
 > > From: Li Chen <chenl311@chinatelecom.cn>
 > > 
 > > The ACPI SPCR (Serial Port Console Redirection) table allows firmware
 > > to specify a preferred serial console device to the operating system.
 > > On ARM64 systems, Linux by default respects this table: even if the
 > > kernel command line does not include a hardware serial console (e.g.,
 > > "console=ttyAMA0"), the kernel still register the serial device
 > > referenced by SPCR as a printk console.
 > > 
 > > While this behavior is standard-compliant, it can lead to situations
 > > where guest console behavior is influenced by platform firmware rather
 > > than user-specified configuration. To make guest console behavior more
 > > predictable and under user control, this patch introduces a machine
 > > option to explicitly disable SPCR table exposure:
 > > 
 > >      -machine spcr=off
 > > 
 > > By default, the option is enabled (spcr=on), preserving existing
 > > behavior. When disabled, QEMU will omit the SPCR table from the guest's
 > > ACPI namespace, ensuring that only consoles explicitly declared in the
 > > kernel command line are registered.
 > > 
 > > Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
 > > Reviewed-by: Bibo Mao <maobibo@loongson.cn>
 > > Acked-by: Michael S. Tsirkin <mst@redhat.com>
 > > ---
 > > 
 > > Changes since V1: add Reviewed-by and Acked-by
 > > 
 > >   hw/arm/virt-acpi-build.c       |  5 ++++-
 > >   hw/core/machine.c              | 22 ++++++++++++++++++++++
 > >   hw/loongarch/virt-acpi-build.c |  4 +++-
 > >   hw/riscv/virt-acpi-build.c     |  5 ++++-
 > >   include/hw/boards.h            |  1 +
 > >   qemu-options.hx                |  5 +++++
 > >   6 files changed, 39 insertions(+), 3 deletions(-)
 > > 
 > 
 > One coding style issue below. With it fixed:
 > 
 > Reviewed-by: Gavin Shan <gshan@redhat.com>

Thanks for your catch! I would fix it in the next version.

Regards,
Li