Message-Id: <C0CB2D0F31868Bindou.takao@jp.fujitsu.com>
Date:	Mon, 26 Jul 2010 18:09:18 -0400
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Enable kdump with EFI boot

Hi all,

The attached patch enables kdump on EFI-boot machine.

[Background]
Current kdump does not work on EFI-boot system because 2nd kernel cannot
find ACPI Table(RSDP). The URL below explains this problem.
http://lists.infradead.org/pipermail/kexec/2010-March/003889.html

This problem can be solved by fixing kexec-tools so that it can set up
struct efi_info correctly in the boot_params for 2nd kernel. However
there is another problem.

When the 1st kernel boots, EFI system table(efi_system_table_t) is
modified by SetVirtualAddressMap, which is one of EFI runtime service.
This runtime changes physical address in EFI system table to virtual
address.

When the 2nd kernel boots, it also receives the same EFI system table,
and the address included in it is already virtual address(1st kernel
rewrote it).  But 2nd kernel does not know that, 2nd kernel thinks it is
a physical address. This causes problems.

For example, the following is a part of efi_init().

c16 = tmp = early_ioremap(efi.systab->fw_vendor, 2);
if (c16) {
    for (i = 0; i < sizeof(vendor) - 1 && *c16; ++i)
        vendor[i] = *c16++;
    vendor[i] = '\0';
} else
    printk(KERN_ERR PFX "Could not map the firmware vendor!\n");

2nd kernel thinks efi.systab->fw_vendor has a physical address and tries
to change it to virtual address, but it is already virtual address, so
this code fails and 2nd kernel hangs up.

[How to fix]
My solution is as follows.
1) Export physical address of each EFI system table entry via debugfs
/sys/kernel/debug/efi/systab/fw_vendor
/sys/kernel/debug/efi/systab/tables
/sys/kernel/debug/efi/systab/runtime

Kexec-tools can get physical address of each entry in EFI system table
via these entries. Kexec tools adds these physical addresses to boot
parameters
ex.)
efi_systab_fw_vendor=0x7a6a1398 efi_systab_tables=0x7a6a2e18 \
efi_systab_runtime=0x7a6a3e18

2) Kernel parses these parameters and use them in efi_init()


So, what this patch is doing is:
- Add debugfs interface for each EFI system table entry
- eif_init() gets physical address of each EFI system table entry from
  boot paramteter instead of the table
- Don't call SetVirtualAddressMap in 2nd kernel because panic occurred
  when SetVirtualAddressMap is called in 2nd kernel. This is called in
  1st kernel, and doesn't need to be called again.

Any comments would be appreciated!

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
---
 arch/x86/kernel/efi.c |  132 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 123 insertions(+), 9 deletions(-)

diff -Nurp linux-2.6.35-rc6.org/arch/x86/kernel/efi.c linux-2.6.35-rc6/arch/x86/kernel/efi.c
--- linux-2.6.35-rc6.org/arch/x86/kernel/efi.c	2010-07-26 12:02:31.216675044 -0400
+++ linux-2.6.35-rc6/arch/x86/kernel/efi.c	2010-07-26 12:17:24.486677191 -0400
@@ -36,6 +36,8 @@
 #include <linux/io.h>
 #include <linux/reboot.h>
 #include <linux/bcd.h>
+#include <linux/crash_dump.h>
+#include <linux/debugfs.h>
 
 #include <asm/setup.h>
 #include <asm/efi.h>
@@ -314,6 +316,97 @@ static void __init print_efi_memmap(void
 }
 #endif  /*  EFI_DEBUG  */
 
+unsigned long systab_fw_vendor_paddr;
+unsigned long systab_runtime_paddr;
+unsigned long systab_tables_paddr;
+
+static struct debugfs_blob_wrapper fw_vendor_blob = {
+	.data		= &systab_fw_vendor_paddr,
+	.size		= sizeof(systab_fw_vendor_paddr),
+};
+
+static struct debugfs_blob_wrapper runtime_blob = {
+	.data		= &systab_runtime_paddr,
+	.size		= sizeof(systab_runtime_paddr),
+};
+
+static struct debugfs_blob_wrapper tables_blob = {
+	.data		= &systab_tables_paddr,
+	.size		= sizeof(systab_tables_paddr),
+};
+
+static int __init setup_systab_fw_vendor_paddr(char *arg)
+{
+	systab_fw_vendor_paddr = simple_strtoul(arg, NULL, 16);
+	return 0;
+}
+early_param("efi_systab_fw_vendor", setup_systab_fw_vendor_paddr);
+
+static int __init setup_systab_runtime_paddr(char *arg)
+{
+	systab_runtime_paddr = simple_strtoul(arg, NULL, 16);
+	return 0;
+}
+early_param("efi_systab_runtime", setup_systab_runtime_paddr);
+
+static int __init setup_systab_tables_paddr(char *arg)
+{
+	systab_tables_paddr = simple_strtoul(arg, NULL, 16);
+	return 0;
+}
+early_param("efi_systab_tables", setup_systab_tables_paddr);
+
+static int create_debug_files_systab (struct dentry *root)
+{
+	struct dentry *systab_dir, *fw_vendor, *runtime, *tables;
+
+	systab_dir = debugfs_create_dir("systab", root);
+	if (!systab_dir)
+		return -1;
+
+	fw_vendor = debugfs_create_blob("fw_vendor", S_IRUGO, systab_dir,
+				            &fw_vendor_blob);
+	if (!fw_vendor)
+		goto err_fw;
+
+	runtime = debugfs_create_blob("runtime", S_IRUGO, systab_dir,
+				            &runtime_blob);
+	if (!runtime)
+		goto err_runtime;
+
+	tables = debugfs_create_blob("tables", S_IRUGO, systab_dir,
+				            &tables_blob);
+	if (tables)
+		return 0;
+
+	debugfs_remove(runtime);
+err_runtime:
+	debugfs_remove(fw_vendor);
+err_fw:
+	debugfs_remove(systab_dir);
+	return -1;
+}
+
+static int crate_debug_files (void)
+{
+	int error;
+	struct dentry *efi_dir;
+
+	efi_dir = debugfs_create_dir("efi", NULL);
+	if (!efi_dir)
+		return -1;
+
+	error = create_debug_files_systab(efi_dir);
+	if (error) {
+		debugfs_remove(efi_dir);
+		return -1;
+	}
+
+	return 0;
+}
+
+late_initcall(crate_debug_files);
+
 void __init efi_init(void)
 {
 	efi_config_table_t *config_tables;
@@ -322,6 +415,7 @@ void __init efi_init(void)
 	char vendor[100] = "unknown";
 	int i = 0;
 	void *tmp;
+	resource_size_t phys_addr;
 
 #ifdef CONFIG_X86_32
 	efi_phys.systab = (efi_system_table_t *)boot_params.efi_info.efi_systab;
@@ -353,7 +447,11 @@ void __init efi_init(void)
 	/*
 	 * Show what we know for posterity
 	 */
-	c16 = tmp = early_ioremap(efi.systab->fw_vendor, 2);
+	if (is_kdump_kernel() && systab_fw_vendor_paddr != 0)
+		phys_addr = systab_fw_vendor_paddr;
+	else
+		phys_addr = efi.systab->fw_vendor;
+	c16 = tmp = early_ioremap(phys_addr, 2);
 	if (c16) {
 		for (i = 0; i < sizeof(vendor) - 1 && *c16; ++i)
 			vendor[i] = *c16++;
@@ -369,8 +467,12 @@ void __init efi_init(void)
 	/*
 	 * Let's see what config tables the firmware passed to us.
 	 */
+	if (is_kdump_kernel() && systab_tables_paddr != 0)
+		phys_addr = systab_tables_paddr;
+	else
+		phys_addr = efi.systab->tables;
 	config_tables = early_ioremap(
-		efi.systab->tables,
+		phys_addr,
 		efi.systab->nr_tables * sizeof(efi_config_table_t));
 	if (config_tables == NULL)
 		printk(KERN_ERR "Could not map EFI Configuration Table!\n");
@@ -418,8 +520,11 @@ void __init efi_init(void)
 	 * address of several of the EFI runtime functions, needed to
 	 * set the firmware into virtual mode.
 	 */
-	runtime = early_ioremap((unsigned long)efi.systab->runtime,
-				sizeof(efi_runtime_services_t));
+	if (is_kdump_kernel() && systab_runtime_paddr != 0)
+		phys_addr = systab_runtime_paddr;
+	else
+		phys_addr = (unsigned long)efi.systab->runtime;
+	runtime = early_ioremap(phys_addr, sizeof(efi_runtime_services_t));
 	if (runtime != NULL) {
 		/*
 		 * We will only need *early* access to the following
@@ -465,6 +570,12 @@ void __init efi_init(void)
 #if EFI_DEBUG
 	print_efi_memmap();
 #endif
+	/* Save original physical address */
+	if (!is_kdump_kernel()) {
+		systab_fw_vendor_paddr = efi.systab->fw_vendor;
+		systab_tables_paddr = efi.systab->tables;
+		systab_runtime_paddr = (unsigned long)efi.systab->runtime;
+	}
 }
 
 static void __init runtime_code_page_mkexec(void)
@@ -544,11 +655,14 @@ void __init efi_enter_virtual_mode(void)
 
 	BUG_ON(!efi.systab);
 
-	status = phys_efi_set_virtual_address_map(
-		memmap.desc_size * memmap.nr_map,
-		memmap.desc_size,
-		memmap.desc_version,
-		memmap.phys_map);
+	if (!is_kdump_kernel())
+		status = phys_efi_set_virtual_address_map(
+			memmap.desc_size * memmap.nr_map,
+			memmap.desc_size,
+			memmap.desc_version,
+			memmap.phys_map);
+	else
+		status = EFI_SUCCESS;
 
 	if (status != EFI_SUCCESS) {
 		printk(KERN_ALERT "Unable to switch EFI into virtual mode "

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