linux-kernel - [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry

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Date:   Fri,  2 Dec 2016 21:54:16 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry_point to kexec'ed kernel

Until now kexec'ed kernel has no clue where to look for DMI entry point.

Pass it via kernel command line parameter in the same way as it's done for ACPI
RSDP.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  5 +++++
 drivers/firmware/dmi_scan.c                     | 14 ++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index be2d6d0..94f219f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -843,6 +843,11 @@
 			The filter can be disabled or changed to another
 			driver later using sysfs.
 
+	dmi_entry_point=	[DMI,EFI,KEXEC]
+			Pass the DMI entry point to the kernel, mostly used
+			on machines running EFI runtime service to boot the
+			second kernel for kdump.
+
 	drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
 			Broken monitors, graphic adapters, KVMs and EDIDless
 			panels may send no or incorrect EDID data sets.
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index b88def6..215843f 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -595,8 +595,22 @@ static int __init dmi_smbios3_present(const u8 *buf)
 	return 1;
 }
 
+#ifdef CONFIG_KEXEC
+static unsigned long dmi_entry_point;
+static int __init setup_dmi_entry_point(char *arg)
+{
+	return kstrtoul(arg, 16, &dmi_entry_point);
+}
+early_param("dmi_entry_point", setup_dmi_entry_point);
+#endif
+
 static resource_size_t __init dmi_get_entry_point(void)
 {
+#ifdef CONFIG_KEXEC
+	if (dmi_entry_point)
+		return dmi_entry_point;
+#endif
+
 	if (efi_enabled(EFI_CONFIG_TABLES)) {
 		/*
 		 * According to the DMTF SMBIOS reference spec v3.0.0, it is
-- 
2.10.2