On Mon, 2023-03-06 at 15:33 -0600, Nathan Lynch via B4 Relay wrote:

quoted

From: Nathan Lynch <redacted>

CHRP and PAPR agree: "In order to make an RTAS call, the operating
system must construct an argument call buffer aligned on an eight
byte
boundary in physically contiguous real memory [...]." (7.2.7
Calling
Mechanism and Conventions).

struct rtas_args is the type used for this argument call buffer.
The
unarchitected 'rets' member happens to produce 8-byte alignment for
the struct on 64-bit targets in practice. But without an alignment
directive the structure will have only 4-byte alignment on 32-bit
targets:

  $ nm b/{before,after}/chrp32/vmlinux | grep rtas_args
  c096881c b rtas_args
  c0968820 b rtas_args

Add an alignment directive to the struct rtas_args declaration so
all
instances have the alignment required by the specs. rtas-types.h no
longer refers to any spinlock types, so drop the spinlock_types.h
inclusion while we're here.

Signed-off-by: Nathan Lynch <redacted>

Reviewed-by: Andrew Donnellan <redacted>

quoted

---
 arch/powerpc/include/asm/rtas-types.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/rtas-types.h

b/arch/powerpc/include/asm/rtas-types.h
index f2ad4a96cbc5..861145c8a021 100644

--- a/arch/powerpc/include/asm/rtas-types.h
+++ b/arch/powerpc/include/asm/rtas-types.h

@@ -2,7 +2,8 @@

 #ifndef _ASM_POWERPC_RTAS_TYPES_H
 #define _ASM_POWERPC_RTAS_TYPES_H
 
-#include <linux/spinlock_types.h>
+#include <linux/compiler_attributes.h>
+#include <linux/sizes.h>
 
 typedef __be32 rtas_arg_t;
 

@@ -12,7 +13,7 @@ struct rtas_args {

        __be32 nret;
        rtas_arg_t args[16];
        rtas_arg_t *rets;     /* Pointer to return values in
args[].
*/
-};
+} __aligned(SZ_8);

Nowhere else in the kernel uses __aligned(SZ_8) over just __aligned(8),
which I suppose would also save an include, but I don't care either
way.

quoted

 
 struct rtas_t {
        unsigned long entry;            /* physical address pointer
*/

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited