[RFC v4][PATCH part-2 10/13] mm/dpt: Function to copy page-table entries for percpu buffer

[Alexandre Chartre <alexandre.chartre@oracle.com>]

Provide functions to copy page-table entries from the kernel page-table
to a decorated page-table for a percpu buffer. A percpu buffer have a
different VA range for each cpu and all them have to be copied.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
 arch/x86/include/asm/dpt.h |  6 ++++++
 arch/x86/mm/dpt.c          | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/arch/x86/include/asm/dpt.h b/arch/x86/include/asm/dpt.h
index 01727ef0577e..fd8c1b84ffe2 100644
--- a/arch/x86/include/asm/dpt.h
+++ b/arch/x86/include/asm/dpt.h
@@ -78,4 +78,10 @@ static inline int dpt_map_module(struct dpt *dpt, char *module_name)
 	(dpt_map(dpt, THIS_MODULE->core_layout.base,	\
 		 THIS_MODULE->core_layout.size))
 
+extern int dpt_map_percpu(struct dpt *dpt, void *percpu_ptr, size_t size);
+extern void dpt_unmap_percpu(struct dpt *dpt, void *percpu_ptr);
+
+#define	DPT_MAP_CPUVAR(dpt, cpuvar)			\
+	dpt_map_percpu(dpt, &cpuvar, sizeof(cpuvar))
+
 #endif
diff --git a/arch/x86/mm/dpt.c b/arch/x86/mm/dpt.c
index c495c9b59b3e..adc59f9ed876 100644
--- a/arch/x86/mm/dpt.c
+++ b/arch/x86/mm/dpt.c
@@ -771,6 +771,44 @@ void dpt_unmap(struct dpt *dpt, void *ptr)
 }
 EXPORT_SYMBOL(dpt_unmap);
 
+void dpt_unmap_percpu(struct dpt *dpt, void *percpu_ptr)
+{
+	void *ptr;
+	int cpu;
+
+	pr_debug("DPT %p: UNMAP PERCPU %px\n", dpt, percpu_ptr);
+	for_each_possible_cpu(cpu) {
+		ptr = per_cpu_ptr(percpu_ptr, cpu);
+		pr_debug("DPT %p: UNMAP PERCPU%d %px\n", dpt, cpu, ptr);
+		dpt_unmap(dpt, ptr);
+	}
+}
+EXPORT_SYMBOL(dpt_unmap_percpu);
+
+int dpt_map_percpu(struct dpt *dpt, void *percpu_ptr, size_t size)
+{
+	int cpu, err;
+	void *ptr;
+
+	pr_debug("DPT %p: MAP PERCPU %px\n", dpt, percpu_ptr);
+	for_each_possible_cpu(cpu) {
+		ptr = per_cpu_ptr(percpu_ptr, cpu);
+		pr_debug("DPT %p: MAP PERCPU%d %px\n", dpt, cpu, ptr);
+		err = dpt_map(dpt, ptr, size);
+		if (err) {
+			/*
+			 * Need to unmap any percpu mapping which has
+			 * succeeded before the failure.
+			 */
+			dpt_unmap_percpu(dpt, percpu_ptr);
+			return err;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(dpt_map_percpu);
+
 /*
  * dpt_create - allocate a page-table and create a corresponding
  * decorated page-table. The page-table is allocated and aligned
-- 
2.18.2