Le 15/03/2024 à 09:38, Christophe Leroy a écrit :

quoted

Le 15/03/2024 à 03:59, Benjamin Gray a écrit :

quoted

The existing patching alias page setup and teardown sections can
be
simplified to make use of the new open_patch_window()
abstraction.

This eliminates the _mm variants of the helpers, consumers no
longer
need to check mm_patch_enabled(), and consumers no longer need to
worry
about synchronization and flushing beyond the changes they make
in the
patching window.

With this patch, the time needed to activate or de-activate
function 
tracer is approx 10% longer on powerpc 8xx.

With the following changes, the performance is restored:

diff --git a/arch/powerpc/lib/code-patching.c 

b/arch/powerpc/lib/code-patching.c
index fd6f8576033a..bc92b85913d8 100644

--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c

@@ -282,13 +282,13 @@ struct patch_window {

   * Interrupts must be disabled for the entire duration of the 
patching. The PIDR
   * is potentially changed during this time.
   */
-static int open_patch_window(void *addr, struct patch_window *ctx)
+static __always_inline int open_patch_window(void *addr, struct 
patch_window *ctx)
  {
  	unsigned long pfn = get_patch_pfn(addr);

  	lockdep_assert_irqs_disabled();

-	ctx->text_poke_addr = (unsigned 
long)__this_cpu_read(cpu_patching_context.addr);
+	ctx->text_poke_addr = (unsigned 
long)__this_cpu_read(cpu_patching_context.addr) & PAGE_MASK;

  	if (!mm_patch_enabled()) {
  		ctx->ptep =
__this_cpu_read(cpu_patching_context.pte);

@@ -331,7 +331,7 @@ static int open_patch_window(void *addr, struct 

patch_window *ctx)
  	return 0;
  }

-static void close_patch_window(struct patch_window *ctx)
+static __always_inline void close_patch_window(struct patch_window
*ctx)
  {
  	lockdep_assert_irqs_disabled();