release the resources of the process at exit(2)/exit_group(2).

arch/x86/kernel/context.S

@@ -4,8 +4,14 @@
 		(X86_CPU_LOCAL_OFFSET_TSS + X86_TSS_OFFSET_SP0)
 
 .text
+
 .globl ihk_mc_switch_context
 ihk_mc_switch_context:
+		/*
+		 * rdi - ihk_mc_kernel_context_t *old_ctx
+		 * rsi - ihk_mc_kernel_context_t *new_ctx
+		 * rdx - void *prev
+		 */
 		pushfq
 		popq	%rax
 		testq	%rdi, %rdi
@@ -35,4 +41,5 @@ ihk_mc_switch_context:
 		popfq
 		movq	8(%rsi), %rbp
 		movq	24(%rsi), %rsi
+		movq	%rdx,%rax
 		retq

arch/x86/kernel/include/arch-memory.h

@@ -42,6 +42,12 @@
 
 #define PT_ENTRIES         512
 
+/* mask of the physical address of the entry to the page table */
+#define	PT_PHYSMASK	(((1UL << 52) - 1) & PAGE_MASK)
+
+#define	PF_PRESENT	0x01	/* entry is valid */
+#define	PF_SIZE		0x80	/* entry points large page */
+
 #define PFL4_PRESENT    0x01
 #define PFL4_WRITABLE   0x02
 #define PFL4_USER       0x04

arch/x86/kernel/memory.c

@@ -557,6 +557,50 @@ struct page_table *ihk_mc_pt_create(void)
 	return pt;
 }
 
+static void destroy_page_table(int level, struct page_table *pt)
+{
+	int ix;
+	unsigned long entry;
+	struct page_table *lower;
+
+	if ((level < 1) || (4 < level)) {
+		panic("destroy_page_table: level is out of range");
+	}
+	if (pt == NULL) {
+		panic("destroy_page_table: pt is NULL");
+	}
+
+	if (level > 1) {
+		for (ix = 0; ix < PT_ENTRIES; ++ix) {
+			entry = pt->entry[ix];
+			if (!(entry & PF_PRESENT)) {
+				/* entry is not valid */
+				continue;
+			}
+			if (entry & PF_SIZE) {
+				/* not a page table */
+				continue;
+			}
+			lower = (struct page_table *)phys_to_virt(entry & PT_PHYSMASK);
+			destroy_page_table(level-1, lower);
+		}
+	}
+
+	arch_free_page(pt);
+	return;
+}
+
+void ihk_mc_pt_destroy(struct page_table *pt)
+{
+	const int level = 4;	/* PML4 */
+
+	/* clear shared entry */
+	memset(pt->entry + PT_ENTRIES / 2, 0, sizeof(pt->entry[0]) * PT_ENTRIES / 2);
+
+	destroy_page_table(level, pt);
+	return;
+}
+
 int ihk_mc_pt_clear_page(page_table_t pt, void *virt)
 {
 	return __clear_pt_page(pt, virt, 0);