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Tsirkin" To: Li Chen Cc: Peter Maydell , Shannon Zhao , Igor Mammedov , Ani Sinha , Eduardo Habkost , Marcel Apfelbaum , =?iso-8859-1?Q?=22Philippe_Mathieu-Daud=E9=22?= , Yanan Wang , Zhao Liu , Song Gao , Bibo Mao , Jiaxun Yang , Sunil V L , Palmer Dabbelt , Alistair Francis , Weiwei Li , qemu-arm@nongnu.org, qemu-devel@nongnu.org, qemu-riscv@nongnu.org Subject: Re: [PATCH] acpi: Add machine option to disable SPCR table Message-ID: <20250422071902-mutt-send-email-mst@kernel.org> References: <87a588wsc9.wl-me@linux.beauty> MIME-Version: 1.0 In-Reply-To: <87a588wsc9.wl-me@linux.beauty> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: q0kBgVkb1V5TP_L6uKCe-9_yk9OOn7JK0eTD1VYDHjg_1745320768 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.411, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-riscv@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-riscv-bounces+qemu-riscv=archiver.kernel.org@nongnu.org Sender: qemu-riscv-bounces+qemu-riscv=archiver.kernel.org@nongnu.org On Tue, Apr 22, 2025 at 03:47:18PM +0800, Li Chen wrote: > From: Li Chen > > 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 The patches look ok to me Acked-by: Michael S. Tsirkin > --- > 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(-) > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > index 3ac8f8e178..f25c3b26ce 100644 > --- a/hw/arm/virt-acpi-build.c > +++ b/hw/arm/virt-acpi-build.c > @@ -940,7 +940,10 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables) > } > > acpi_add_table(table_offsets, tables_blob); > - spcr_setup(tables_blob, tables->linker, vms); > + > + if (ms->enable_spcr) { > + spcr_setup(tables_blob, tables->linker, vms); > + } > > acpi_add_table(table_offsets, tables_blob); > build_dbg2(tables_blob, tables->linker, vms); > diff --git a/hw/core/machine.c b/hw/core/machine.c > index 63c6ef93d2..d56f44f4e8 100644 > --- a/hw/core/machine.c > +++ b/hw/core/machine.c > @@ -590,6 +590,20 @@ static void machine_set_nvdimm(Object *obj, bool value, Error **errp) > ms->nvdimms_state->is_enabled = value; > } > > +static bool machine_get_spcr(Object *obj, Error **errp) > +{ > + MachineState *ms = MACHINE(obj); > + > + return ms->enable_spcr; > +} > + > +static void machine_set_spcr(Object *obj, bool value, Error **errp) > +{ > + MachineState *ms = MACHINE(obj); > + > + ms->enable_spcr = value; > +} > + > static bool machine_get_hmat(Object *obj, Error **errp) > { > MachineState *ms = MACHINE(obj); > @@ -1294,6 +1308,14 @@ static void machine_initfn(Object *obj) > "Table (HMAT)"); > } > > + /* SPCR */ > + ms->enable_spcr = true; > + object_property_add_bool(obj, "spcr", machine_get_spcr, machine_set_spcr); > + object_property_set_description(obj, "spcr", > + "Set on/off to enable/disable " > + "ACPI Serial Port Console Redirection " > + "Table (spcr)"); > + > /* default to mc->default_cpus */ > ms->smp.cpus = mc->default_cpus; > ms->smp.max_cpus = mc->default_cpus; > diff --git a/hw/loongarch/virt-acpi-build.c b/hw/loongarch/virt-acpi-build.c > index fced6c445a..0e437bcf25 100644 > --- a/hw/loongarch/virt-acpi-build.c > +++ b/hw/loongarch/virt-acpi-build.c > @@ -557,7 +557,9 @@ static void acpi_build(AcpiBuildTables *tables, MachineState *machine) > acpi_add_table(table_offsets, tables_blob); > build_srat(tables_blob, tables->linker, machine); > acpi_add_table(table_offsets, tables_blob); > - spcr_setup(tables_blob, tables->linker, machine); > + > + if (machine->enable_spcr) > + spcr_setup(tables_blob, tables->linker, machine); > > if (machine->numa_state->num_nodes) { > if (machine->numa_state->have_numa_distance) { > diff --git a/hw/riscv/virt-acpi-build.c b/hw/riscv/virt-acpi-build.c > index 1ad6800508..7f6d221c63 100644 > --- a/hw/riscv/virt-acpi-build.c > +++ b/hw/riscv/virt-acpi-build.c > @@ -680,7 +680,10 @@ static void virt_acpi_build(RISCVVirtState *s, AcpiBuildTables *tables) > build_rhct(tables_blob, tables->linker, s); > > acpi_add_table(table_offsets, tables_blob); > - spcr_setup(tables_blob, tables->linker, s); > + > + if (ms->enable_spcr) { > + spcr_setup(tables_blob, tables->linker, s); > + } > > acpi_add_table(table_offsets, tables_blob); > { > diff --git a/include/hw/boards.h b/include/hw/boards.h > index f22b2e7fc7..cdf2791a50 100644 > --- a/include/hw/boards.h > +++ b/include/hw/boards.h > @@ -444,6 +444,7 @@ struct MachineState { > SmpCache smp_cache; > struct NVDIMMState *nvdimms_state; > struct NumaState *numa_state; > + bool enable_spcr; > }; > > /* > diff --git a/qemu-options.hx b/qemu-options.hx > index dc694a99a3..953680595f 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -38,6 +38,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \ > " nvdimm=on|off controls NVDIMM support (default=off)\n" > " memory-encryption=@var{} memory encryption object to use (default=none)\n" > " hmat=on|off controls ACPI HMAT support (default=off)\n" > + " spcr=on|off controls ACPI SPCR support (default=on)\n" > #ifdef CONFIG_POSIX > " aux-ram-share=on|off allocate auxiliary guest RAM as shared (default: off)\n" > #endif > @@ -105,6 +106,10 @@ SRST > Enables or disables ACPI Heterogeneous Memory Attribute Table > (HMAT) support. The default is off. > > + ``spcr=on|off`` > + Enables or disables ACPI Serial Port Console Redirection Table > + (SPCR) support. The default is on. > + > ``aux-ram-share=on|off`` > Allocate auxiliary guest RAM as an anonymous file that is > shareable with an external process. This option applies to > -- > 2.49.0