[PATCH] kdump, proc/vmcore: fix building without CONFIG_ARCH_HAS_MEM_ENCRYPT

[Arnd Bergmann <arnd@arndb.de>]

We get a link failure when calling copy_oldmem_page_encrypted()
when the compiler fails to do constant-propagation of the
sme_active() result into read_from_oldmem:

fs/proc/vmcore.o: In function `read_from_oldmem.part.0':
vmcore.c:(.text+0xb7): undefined reference to `copy_oldmem_page_encrypted'

Adding an IS_ENABLED() check means the compiler will always
know when it cannot be enabled.

Fixes: 992b649a3f01 ("kdump, proc/vmcore: Enable kdumping encrypted memory with SME enabled")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
There may be a better way of doing this, not sure what kinds
of assumptions we want to make here.
---
 fs/proc/vmcore.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index d469ce9d8c0c..92e1e520a52d 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -123,7 +123,9 @@ static ssize_t read_from_oldmem(char *buf, size_t count,
 		if (pfn_is_ram(pfn) == 0)
 			memset(buf, 0, nr_bytes);
 		else {
-			if (encrypted)
+			if (IS_ENABLED(CONFIG_X86_64) &&
+			    IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT) &&
+			    encrypted)
 				tmp = copy_oldmem_page_encrypted(pfn, buf,
 								 nr_bytes,
 								 offset,
-- 
2.18.0