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powerpc/rtas: ensure 8-byte alignment for struct rtas_args

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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 <nathanl@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230220-rtas-queue-for-6-4-v1-1-010e4416f13f@linux.ibm.com
This commit is contained in:
Nathan Lynch 2023-03-06 15:33:40 -06:00 committed by Michael Ellerman
parent 05dce4ba12
commit f40b0f6c5c
1 changed files with 2 additions and 2 deletions
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4
arch/powerpc/include/asm/rtas-types.h
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@ -2,7 +2,7 @@
#ifndef _ASM_POWERPC_RTAS_TYPES_H
#define _ASM_POWERPC_RTAS_TYPES_H
#include <linux/spinlock_types.h>
#include <linux/compiler_attributes.h>
typedef __be32 rtas_arg_t;
@ -12,7 +12,7 @@ struct rtas_args {
__be32 nret;
rtas_arg_t args[16];
rtas_arg_t *rets; /* Pointer to return values in args[]. */
};
} __aligned(8);
struct rtas_t {
unsigned long entry; /* physical address pointer */