Messages in this thread Patch in this message | | | From | Baoquan He <> | Subject | [PATCH v4 1/3] x86/boot: Add xloadflags bits for 5-level kernel checking | Date | Thu, 9 May 2019 09:36:42 +0800 |
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The current kernel supports 5-level paging mode, and supports dynamically choosing paging mode during bootup according to kernel image, hardware and kernel parameter setting. This flexibility brings several issues to kexec/kdump: 1) Dynamic switching between paging modes requires code change in target kernel. So we can't do kexec-jumping from 5-level kernel to old 4-level kernel which lacks the code change.
2) Kexec jumping from 5-level kernel to 4-level kernel would fail, if kexec loading puts kernel image above 64 TB of memory. Because kexec loading searches area to put kernel from top to down in system RAM, the 2nd kernel will be loaded above 64 TB if the amount of system RAM is bigger than 64 TB. Here no need to worry about kexec_file loading, because it searches area from bottom to up, and can always find area below 4 GB.
Solution:
Add two bits XLF_5LEVEL and XLF_5LEVEL_ENABLED for 5-level kernel. - Bit XLF_5LEVEL indicates if 5-level related code is contained in this kernel. - Bit XLF_5LEVEL_ENABLED indicates if CONFIG_X86_5LEVEL=y is set.
a) For issue 1), need check if XLF_5LEVEL is set, otherwise print out error message. - This checking need be added in kernel, for the code of kexec_file loading; - And also need be added into kexec_tools utility, for kexec loading.
b) For issue 2), need check if both XLF_5LEVEL and XLF_5LEVEL_ENABLED are set, otherwise print out error message. - This only need be done in kexec_tools utility, because kexec loading does the searching in user space kexec_tools.
So here add XLF_5LEVEL and XLF_5LEVEL_ENABLED into xloadflags. The later code will check XLF_5LEVEL bit in kexec_file implementation of kernel. And the kexec_tools code will check both XLF_5LEVEL and XLF_5LEVEL_ENABLED for kexec loading.
Signed-off-by: Baoquan He <bhe@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/boot/header.S | 12 +++++++++++- arch/x86/include/uapi/asm/bootparam.h | 2 ++ 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index 850b8762e889..be19f4199727 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -419,7 +419,17 @@ xloadflags: # define XLF4 0 #endif - .word XLF0 | XLF1 | XLF23 | XLF4 +#ifdef CONFIG_X86_64 +#ifdef CONFIG_X86_5LEVEL +#define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED) +#else +#define XLF56 XLF_5LEVEL +#endif +#else +#define XLF56 0 +#endif + + .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56 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 60733f137e9a..c895df5482c5 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -29,6 +29,8 @@ #define XLF_EFI_HANDOVER_32 (1<<2) #define XLF_EFI_HANDOVER_64 (1<<3) #define XLF_EFI_KEXEC (1<<4) +#define XLF_5LEVEL (1<<5) +#define XLF_5LEVEL_ENABLED (1<<6) #ifndef __ASSEMBLY__ -- 2.17.2
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