On Fri, Sep 8, 2023 at 6:28 AM Hari Bathini <hbath...@linux.ibm.com> wrote:
>
> patch_instruction() entails setting up pte, patching the instruction,
> clearing the pte and flushing the tlb. If multiple instructions need
> to be patched, every instruction would have to go through the above
> drill unnecessarily. Instead, introduce function patch_instructions()
> that sets up the pte, clears the pte and flushes the tlb only once per
> page range of instructions to be patched. This adds a slight overhead
> to patch_instruction() call while improving the patching time for
> scenarios where more than one instruction needs to be patched.
>
> Signed-off-by: Hari Bathini <hbath...@linux.ibm.com>
I didn't see this one when I reviewed 1/5. Please ignore that comment.
[...]
> @@ -307,11 +312,22 @@ static int __do_patch_instruction_mm(u32 *addr,
> ppc_inst_t instr)
>
> orig_mm = start_using_temp_mm(patching_mm);
>
> - err = __patch_instruction(addr, instr, patch_addr);
> + while (len > 0) {
> + instr = ppc_inst_read(code);
> + ilen = ppc_inst_len(instr);
> + err = __patch_instruction(addr, instr, patch_addr);
It appears we are still repeating a lot of work here. For example, with
fill_insn == true, we don't need to repeat ppc_inst_read().
Can we do this with a memcpy or memset like functions?
> + /* hwsync performed by __patch_instruction (sync) if
> successful */
> + if (err) {
> + mb(); /* sync */
> + break;
> + }
>
> - /* hwsync performed by __patch_instruction (sync) if successful */
> - if (err)
> - mb(); /* sync */
> + len -= ilen;
> + patch_addr = patch_addr + ilen;
> + addr = (void *)addr + ilen;
> + if (!fill_insn)
> + code = code + ilen;
It took me a while to figure out what "fill_insn" means. Maybe call it
"repeat_input" or something?
Thanks,
Song
> + }
>
> /* context synchronisation performed by __patch_instruction (isync or
> exception) */
> stop_using_temp_mm(patching_mm, orig_mm);
> @@ -328,16 +344,21 @@ static int __do_patch_instruction_mm(u32 *addr,
> ppc_inst_t instr)
> return err;
> }
>
