pmem: fix BUG() error in pmem.h:48 on X86_32

After 'commit fc0c2028135c ("x86, pmem: use memcpy_mcsafe()
for memcpy_from_pmem()")', probing a PMEM device hits the BUG()
error below on X86_32 kernel.

 kernel BUG at include/linux/pmem.h:48!

memcpy_from_pmem() calls arch_memcpy_from_pmem(), which is
unimplemented since CONFIG_ARCH_HAS_PMEM_API is undefined on
X86_32.

Fix the BUG() error by adding default_memcpy_from_pmem().

Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>

1 files changed, 16 insertions, 6 deletions

diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index ac6d872ce067..57d146fe44dd 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -72,6 +72,18 @@ static inline void arch_invalidate_pmem(void __pmem *addr, size_t size)
 }
 #endif
 
+static inline bool arch_has_pmem_api(void)
+{
+        return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API);
+}
+
+static inline int default_memcpy_from_pmem(void *dst, void __pmem const *src,
+                size_t size)
+{
+        memcpy(dst, (void __force *) src, size);
+        return 0;
+}
+
 /*
  * memcpy_from_pmem - read from persistent memory with error handling
  * @dst: destination buffer
@@ -83,12 +95,10 @@ static inline void arch_invalidate_pmem(void __pmem *addr, size_t size)
 static inline int memcpy_from_pmem(void *dst, void __pmem const *src,
                 size_t size)
 {
-        return arch_memcpy_from_pmem(dst, src, size);
-}
-
-static inline bool arch_has_pmem_api(void)
-{
-        return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API);
+        if (arch_has_pmem_api())
+                return arch_memcpy_from_pmem(dst, src, size);
+        else
+                return default_memcpy_from_pmem(dst, src, size);
 }
 
 /**