[PATCH] powerpc/code-patching: Perform hwsync in __patch_instruction() in case of failure

[PATCH] powerpc/code-patching: Perform hwsync in __patch_instruction() in case of failure

[Christophe Leroy]

Commit c28c15b6d28a ("powerpc/code-patching: Use temporary mm for
Radix MMU") added a hwsync for when __patch_instruction() fails,
we results in a quite odd unbalanced logic.

Instead of calling mb() when __patch_instruction() returns an error,
call mb() in the __patch_instruction()'s error path directly.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Christopher M. Riedl <cmr@bluescreens.de>
---
 arch/powerpc/lib/code-patching.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index b00112d7ad46..7a47a871e6b8 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -38,6 +38,7 @@ static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr
 	return 0;
 
 failed:
+	mb();  /* sync */
 	return -EPERM;
 }
 
@@ -309,10 +310,6 @@ static int __do_patch_instruction_mm(u32 *addr, ppc_inst_t instr)
 
 	err = __patch_instruction(addr, instr, patch_addr);
 
-	/* hwsync performed by __patch_instruction (sync) if successful */
-	if (err)
-		mb();  /* sync */
-
 	/* context synchronisation performed by __patch_instruction (isync or exception) */
 	stop_using_temp_mm(patching_mm, orig_mm);
 
-- 
2.41.0

Re: [PATCH] powerpc/code-patching: Perform hwsync in __patch_instruction() in case of failure

[Michael Ellerman]

On Sat, 07 Oct 2023 12:46:19 +0200, Christophe Leroy wrote:
> Commit c28c15b6d28a ("powerpc/code-patching: Use temporary mm for
> Radix MMU") added a hwsync for when __patch_instruction() fails,
> we results in a quite odd unbalanced logic.
> 
> Instead of calling mb() when __patch_instruction() returns an error,
> call mb() in the __patch_instruction()'s error path directly.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/code-patching: Perform hwsync in __patch_instruction() in case of failure
      https://git.kernel.org/powerpc/c/74726fda9fe306f848088ef73ec266cae0470d5b

cheers