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authorArthur Heymans <arthur@aheymans.xyz>2019-11-18 11:19:31 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-01-14 21:46:48 +0100
commite4924ee263b015cc2e397ca871d870925e2673b4 (patch)
treed12c1388810f353196fc882be8a4a4a6b0250686 /drivers
parentc6e7af0515daca800d84b9cfa1bf19e53c4f5bc3 (diff)
firmware: google: Probe for a GSMI handler in firmware
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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/firmware/google/gsmi.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c
index 974c769b75cf..5b2011ebbe26 100644
--- a/drivers/firmware/google/gsmi.c
+++ b/drivers/firmware/google/gsmi.c
@@ -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;
}