[PATCH 2/2 v3] kdump,vmcoreinfo: Export the value of sme mask to vmcoreinfo

[Lianbo Jiang]

For AMD machine with SME feature, makedumpfile tools need to know
whether the crash kernel was encrypted or not. If SME is enabled
in the first kernel, the crash kernel's page table(pgd/pud/pmd/pte)
contains the memory encryption mask, so need to remove the sme mask
to obtain the true physical address.

Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
---
 arch/x86/kernel/machine_kexec_64.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 4c8acdfdc5a7..1860fe24117d 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -352,10 +352,24 @@ void machine_kexec(struct kimage *image)
 
 void arch_crash_save_vmcoreinfo(void)
 {
+	u64 sme_mask = sme_me_mask;
+
 	VMCOREINFO_NUMBER(phys_base);
 	VMCOREINFO_SYMBOL(init_top_pgt);
 	vmcoreinfo_append_str("NUMBER(pgtable_l5_enabled)=%d\n",
 			pgtable_l5_enabled());
+	/*
+	 * Currently, the local variable 'sme_mask' stores the value of
+	 * sme_me_mask(bit 47), and also write the value of sme_mask to
+	 * the vmcoreinfo.
+	 * If need, the bit(sme_mask) might be redefined in the future,
+	 * but the 'bit63' will be reserved.
+	 * For example:
+	 * [ misc	   ][ enc bit  ][ other misc SME info       ]
+	 * 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
+	 * 63   59   55   51   47   43   39   35   31   27   ... 3
+	 */
+	VMCOREINFO_NUMBER(sme_mask);
 
 #ifdef CONFIG_NUMA
 	VMCOREINFO_SYMBOL(node_data);
-- 
2.17.1