[tip:x86/mm] kdump, vmcoreinfo: Export pgtable_l5_enabled value

[tip-bot for Baoquan He]

Commit-ID:  c100a583601d357f923c41af5434dc1f8d07890f
Gitweb:     https://git.kernel.org/tip/c100a583601d357f923c41af5434dc1f8d07890f
Author:     Baoquan He <bhe@xxxxxxxxxx>
AuthorDate: Fri, 2 Mar 2018 13:18:01 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 12 Mar 2018 09:43:56 +0100

kdump, vmcoreinfo: Export pgtable_l5_enabled value

User-space utilities examining crash-kernels need to know if the
crashed kernel was in 5-level paging mode or not.

So write 'pgtable_l5_enabled' to vmcoreinfo, which covers these
three cases:

  pgtable_l5_enabled == 0 when:
   - Compiled with !CONFIG_X86_5LEVEL
   - Compiled with CONFIG_X86_5LEVEL=y while CPU has no 'la57' flag

  pgtable_l5_enabled != 0 when:
   - Compiled with CONFIG_X86_5LEVEL=y and CPU has 'la57' flag

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: douly.fnst@xxxxxxxxxxxxxx
Cc: dyoung@xxxxxxxxxx
Cc: ebiederm@xxxxxxxxxxxx
Cc: kirill.shutemov@xxxxxxxxxxxxxxx
Cc: vgoyal@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20180302051801.19594-1-bhe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/machine_kexec_64.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 3b7427aa7d85..02f913cb27b5 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -350,6 +350,7 @@ void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_NUMBER(phys_base);
 	VMCOREINFO_SYMBOL(init_top_pgt);
+	VMCOREINFO_NUMBER(pgtable_l5_enabled);
 
 #ifdef CONFIG_NUMA
 	VMCOREINFO_SYMBOL(node_data);