Commit f5a4af3c authored by Liu Wei's avatar Liu Wei Committed by Catalin Marinas
Browse files

ACPI: Add acpi=nospcr to disable ACPI SPCR as default console on ARM64 



For varying privacy and security reasons, sometimes we would like to
completely silence the _serial_ console, and only enable it when needed.

But there are many existing systems that depend on this _serial_ console,
so add acpi=nospcr to disable console in ACPI SPCR table as default
_serial_ console.

Signed-off-by: default avatarLiu Wei <liuwei09@cestc.cn>
Suggested-by: default avatarPrarit Bhargava <prarit@redhat.com>
Suggested-by: default avatarWill Deacon <will@kernel.org>
Suggested-by: default avatarAndrew Lunn <andrew@lunn.ch>
Reviewed-by: default avatarHanjun Guo <guohanjun@huawei.com>
Reviewed-by: default avatarPrarit Bhargava <prarit@redhat.com>
Link: https://lore.kernel.org/r/20240625030504.58025-1-liuwei09@cestc.cn


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent bfe3f0df

Documentation/admin-guide/kernel-parameters.txt

+7 −3
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
	acpi=		[HW,ACPI,X86,ARM64,RISCV64,EARLY]

			Advanced Configuration and Power Interface

			Format: { force | on | off | strict | noirq | rsdt |

				  copy_dsdt }

				  copy_dsdt | nospcr }

			force -- enable ACPI if default was off

			on -- enable ACPI but allow fallback to DT [arm64,riscv64]

			off -- disable ACPI if default was on
@@ -21,8 +21,12 @@ 
				strictly ACPI specification compliant.

			rsdt -- prefer RSDT over (default) XSDT

			copy_dsdt -- copy DSDT to memory

			For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or

			"acpi=force" are available

			nospcr -- disable console in ACPI SPCR table as

				default _serial_ console on ARM64

			For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or

			"acpi=nospcr" are available

			For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force"

			are available



			See also Documentation/power/runtime_pm.rst, pci=noacpi

arch/arm64/kernel/acpi.c

+17 −1
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ EXPORT_SYMBOL(acpi_pci_disabled); 
static bool param_acpi_off __initdata;

static bool param_acpi_on __initdata;

static bool param_acpi_force __initdata;

static bool param_acpi_nospcr __initdata;



static int __init parse_acpi(char *arg)

{
@@ -58,6 +59,8 @@ static int __init parse_acpi(char *arg) 
		param_acpi_on = true;

	else if (strcmp(arg, "force") == 0) /* force ACPI to be enabled */

		param_acpi_force = true;

	else if (strcmp(arg, "nospcr") == 0) /* disable SPCR as default console */

		param_acpi_nospcr = true;

	else

		return -EINVAL;	/* Core will print when we return error */
@@ -237,7 +240,20 @@ void __init acpi_boot_table_init(void) 
			acpi_put_table(facs);

		}

#endif

		acpi_parse_spcr(earlycon_acpi_spcr_enable, true);



		/*

		 * For varying privacy and security reasons, sometimes need

		 * to completely silence the serial console output, and only

		 * enable it when needed.

		 * But there are many existing systems that depend on this

		 * behaviour, use acpi=nospcr to disable console in ACPI SPCR

		 * table as default serial console.

		 */

		acpi_parse_spcr(earlycon_acpi_spcr_enable,

			!param_acpi_nospcr);

		pr_info("Use ACPI SPCR as default console: %s\n",

				param_acpi_nospcr ? "No" : "Yes");



		if (IS_ENABLED(CONFIG_ACPI_BGRT))

			acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);

	}