[tip:x86/efi-kexec] x86: Add xloadflags bit for EFI runtime support on kexec

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Commit-ID:  456a29ddada79198c5965300e04103c40c481f62
Gitweb:     http://git.kernel.org/tip/456a29ddada79198c5965300e04103c40c481f62
Author:     Dave Young <dyoung@xxxxxxxxxx>
AuthorDate: Fri, 20 Dec 2013 18:02:20 +0800
Committer:  Matt Fleming <matt.fleming@xxxxxxxxx>
CommitDate: Sun, 29 Dec 2013 13:09:06 +0000

x86: Add xloadflags bit for EFI runtime support on kexec

Old kexec-tools can not load new kernels. The reason is kexec-tools does
not fill efi_info in x86 setup header previously, thus EFI failed to
initialize.  In new kexec-tools it will by default to fill efi_info and
pass other EFI required infomation to 2nd kernel so kexec kernel EFI
initialization can succeed finally.

To prevent from breaking userspace, add a new xloadflags bit so
kexec-tools can check the flag and switch to old logic.

Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
Acked-by: Borislav Petkov <bp@xxxxxxx>
Tested-by: Toshi Kani <toshi.kani@xxxxxx>
Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx>
---
 Documentation/x86/boot.txt            | 3 +++
 arch/x86/boot/header.S                | 9 ++++++++-
 arch/x86/include/uapi/asm/bootparam.h | 1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index f4f268c..cb81741d 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -608,6 +608,9 @@ Protocol:       2.12+
 	- If 1, the kernel supports the 64-bit EFI handoff entry point
           given at handover_offset + 0x200.
 
+  Bit 4 (read): XLF_EFI_KEXEC
+	- If 1, the kernel supports kexec EFI boot with EFI runtime support.
+
 Field name:	cmdline_size
 Type:		read
 Offset/size:	0x238/4
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 9ec06a1..ec3b8ba 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -391,7 +391,14 @@ xloadflags:
 #else
 # define XLF23 0
 #endif
-			.word XLF0 | XLF1 | XLF23
+
+#if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC)
+# define XLF4 XLF_EFI_KEXEC
+#else
+# define XLF4 0
+#endif
+
+			.word XLF0 | XLF1 | XLF23 | XLF4
 
 cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
                                                 #added with boot protocol
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index 64fe421..225b098 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -24,6 +24,7 @@
 #define XLF_CAN_BE_LOADED_ABOVE_4G	(1<<1)
 #define XLF_EFI_HANDOVER_32		(1<<2)
 #define XLF_EFI_HANDOVER_64		(1<<3)
+#define XLF_EFI_KEXEC			(1<<4)
 
 #ifndef __ASSEMBLY__
 
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