linux-kernel - [PATCH] kdump, vmcoreinfo: Export value to tell if 5-level is enabled

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Date:   Fri,  2 Mar 2018 13:18:01 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, tglx@...utronix.de,
        kirill.shutemov@...ux.intel.com, hpa@...or.com, dyoung@...hat.com,
        x86@...nel.org, ebiederm@...ssion.com, douly.fnst@...fujitsu.com,
        vgoyal@...hat.com, Baoquan He <bhe@...hat.com>
Subject: [PATCH] kdump, vmcoreinfo: Export value to tell if 5-level is enabled

Userspace utility needs to know if the corrupted kernel is in
5-level paging mode. So write 'pgtable_l5_enabled' to vmcoreinfo.
It covers below three cases:
  pgtable_l5_enabled == 0 when
  Compile kernel with CONFIG_X86_5LEVEL=n
  Compile with CONFIG_X86_5LEVEL=y while cpu has no 'la57' flag

  pgtable_l5_enabled != 0 when
  Compile with CONFIG_X86_5LEVEL=y and cpu has 'la57' flag

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 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 1f790cf9d38f..5f3545eaa76a 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);
-- 
2.13.6