memset() is patched after initialisation to activate the
optimised part which uses cache instructions.
Today we have a 'b 2f' to skip the optimised patch, which then gets
replaced by a NOP, implying a useless cycle consumption.
As we have a 'bne 2f' just before, we could use that instruction
for the live patching, hence removing the need to have a
dedicated 'b 2f' to be replaced by a NOP.
This patch changes the 'bne 2f' by a 'b 2f'. During init, that
'b 2f' is then replaced by 'bne 2f'
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
arch/powerpc/kernel/setup_32.c | 7 ++++++-
arch/powerpc/lib/copy_32.S | 7 +++++--
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 2f88f6cf1a42..51ebc01fff52 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -98,6 +98,9 @@ extern unsigned int memset_nocache_branch; /* Insn to be
replaced by NOP */
notrace void __init machine_init(u64 dt_ptr)
{
+ unsigned int *addr = &memset_nocache_branch;
+ unsigned long insn;
+
/* Configure static keys first, now that we're relocated. */
setup_feature_keys();
@@ -105,7 +108,9 @@ notrace void __init machine_init(u64 dt_ptr)
udbg_early_init();
patch_instruction((unsigned int *)&memcpy, PPC_INST_NOP);
- patch_instruction(&memset_nocache_branch, PPC_INST_NOP);
+
+ insn = create_cond_branch(addr, branch_target(addr), 0x820000);
+ patch_instruction(addr, insn); /* replace b by bne cr0 */
/* Do some early initialization based on the flat device tree */
early_init_devtree(__va(dt_ptr));
diff --git a/arch/powerpc/lib/copy_32.S b/arch/powerpc/lib/copy_32.S
index 05aaee20590f..da425bb6b369 100644
--- a/arch/powerpc/lib/copy_32.S
+++ b/arch/powerpc/lib/copy_32.S
@@ -103,9 +103,12 @@ _GLOBAL(memset)
add r5,r0,r5
subf r6,r0,r3
cmplwi 0,r4,0
- bne 2f /* Use normal procedure if r4 is not zero */
+ /*
+ * Skip optimised bloc until cache is enabled. Will be replaced
+ * by 'bne' during boot to use normal procedure if r4 is not zero
+ */
_GLOBAL(memset_nocache_branch)
- b 2f /* Skip optimised bloc until cache is enabled */
+ b 2f
clrlwi r7,r6,32-LG_CACHELINE_BYTES
add r8,r7,r5
--
2.13.3
