firmware: google: Probe for a GSMI handler in firmware (e4924ee2) · Commits · 戴 / test

Currently this driver is loaded if the DMI string matches coreboot and has a proper smi_command in the ACPI FADT table, but a GSMI handler in SMM is an optional feature in coreboot. So probe for a SMM GSMI handler before initializing the driver. If the smihandler leaves the calling argument in %eax in the SMM save state untouched that generally means the is no handler for GSMI. Signed-off-by:

Arthur Heymans <arthur@aheymans.xyz> Signed-off-by:

Patrick Rudolph <patrick.rudolph@9elements.com> Link: https://lore.kernel.org/r/20191118101934.22526-4-patrick.rudolph@9elements.com Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/google/gsmi.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -76,6 +76,7 @@
		#define GSMI_CMD_LOG_S0IX_RESUME 0x0b
		#define GSMI_CMD_CLEAR_CONFIG 0x20
		#define GSMI_CMD_HANDSHAKE_TYPE 0xC1
		#define GSMI_CMD_RESERVED 0xff

		/* Magic entry type for kernel events */
		#define GSMI_LOG_ENTRY_TYPE_KERNEL 0xDEAD
		@@ -746,6 +747,7 @@ MODULE_DEVICE_TABLE(dmi, gsmi_dmi_table);
		static __init int gsmi_system_valid(void)
		{
		u32 hash;
		u16 cmd, result;

		if (!dmi_check_system(gsmi_dmi_table))
		return -ENODEV;
		@@ -780,6 +782,23 @@ static __init int gsmi_system_valid(void)
		return -ENODEV;
		}

		/* Test the smihandler with a bogus command. If it leaves the
		* calling argument in %ax untouched, there is no handler for
		* GSMI commands.
		*/
		cmd = GSMI_CALLBACK \| GSMI_CMD_RESERVED << 8;
		asm volatile (
		"outb %%al, %%dx\n\t"
		: "=a" (result)
		: "0" (cmd),
		"d" (acpi_gbl_FADT.smi_command)
		: "memory", "cc"
		);
		if (cmd == result) {
		pr_info("gsmi: no gsmi handler in firmware\n");
		return -ENODEV;
		}

		/* Found */
		return 0;
		}

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