[PATCH 2/2] kexec: add a pmd huge entry condition during the page table

[zhongjiang]

From: zhong jiang <zhongjiang at huawei.com>

when image is loaded into kernel, we need set up page table for it. and 
all valid pfn also set up new mapping. it will tend to establish a pmd 
page table in the form of a large page if pud_present is true. relocate_kernel 
points to code segment can locate in the pmd huge entry in init_transtion_pgtable. 
therefore, we need to take the situation into account.

Signed-off-by: zhong jiang <zhongjiang at huawei.com>
---
 arch/x86/kernel/machine_kexec_64.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 5a294e4..c33e344 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -14,6 +14,7 @@
 #include <linux/gfp.h>
 #include <linux/reboot.h>
 #include <linux/numa.h>
+#include <linux/hugetlb.h>
 #include <linux/ftrace.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
@@ -34,6 +35,17 @@ static struct kexec_file_ops *kexec_file_loaders[] = {
 };
 #endif
 
+static void split_pmd(pmd_t *pmd, pte_t *pte)
+{
+	unsigned long pfn = pmd_pfn(*pmd);
+	int i = 0;
+
+	do {
+		set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
+		pfn++;
+	} while (pte++, i++, i < PTRS_PER_PTE);
+}
+
 static void free_transition_pgtable(struct kimage *image)
 {
 	free_page((unsigned long)image->arch.pud);
@@ -68,15 +80,19 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
 	}
 	pmd = pmd_offset(pud, vaddr);
-	if (!pmd_present(*pmd)) {
+	if (!pmd_present(*pmd) || pmd_huge(*pmd)) {
 		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pte)
 			goto err;
 		image->arch.pte = pte;
-		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
+		if (pmd_huge(*pmd))
+			split_pmd(pmd, pte);
+		else
+			set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
 	}
 	pte = pte_offset_kernel(pmd, vaddr);
 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
+
 	return 0;
 err:
 	free_transition_pgtable(image);
-- 
1.8.3.1