[PATCH OLK-5.10 1/2] random: Workaround for performance degrade

28 Apr 2024

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9K8D1
--------------------------------
A performance degrade is observed on boards with certain chips. Debugging
shows that degrade is caused by the two line in drivers/char/random.c.
The root cause of why these two lines would cause such degrade is
still unknown.
This patch is meant to be a workaround for said issue.
Fixes: 6c315cc252ce ("random: use first 128 bits of input as fast init")
Signed-off-by: GUO Zihua guozihua@huawei.com
---
 drivers/char/Kconfig  |   9 +++
 drivers/char/random.c | 163 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 171 insertions(+), 1 deletion(-)

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 677e16195d32..872e6f661998 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -513,4 +513,13 @@ config RANDOM_TRUST_BOOTLOADER
      believe its RNG facilities may be faulty. This may also be configured
      at boot time with "random.trust_bootloader=on/off".
+config RTOS_FIX_RANDOM_PERFORMANCE
+	bool "Fix random performance degrade on certain platform"
+	depends on ARM
+	default n
+	help
+	  It's observed that there is a performance degrade related to random on
+	  system with certain chip. The root cause is unknown and this config is
+	  meant to be a workaround for that issue.
+
 endmenu
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 6aa1c013a2b7..6c0ff6a5a524 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -347,8 +347,10 @@ static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
    	spin_lock_irqsave(&base_crng.lock, flags);
    	ready = crng_ready();
    	if (!ready) {
+#ifndef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
    		if (crng_init == CRNG_EMPTY)
    			extract_entropy(base_crng.key, sizeof(base_crng.key));
+#endif
    		crng_fast_key_erasure(base_crng.key, chacha_state,
    				      random_data, random_data_len);
    	}
@@ -392,6 +394,129 @@ static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
    local_unlock_irqrestore(&crngs.lock, flags);
 }
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+/*
+ * Dummy function acting as a placeholder to 1380 performance degrade.
+ * It contains 112 nops, which is exactly the instruction count of the original
+ * function crng_pre_init_inject.
+ */
+static void __used dummy(const void *input, size_t len, bool account)
+{
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+	__asm__ __volatile__ ("nop");
+}
+#endif // CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+
 static void _get_random_bytes(void *buf, size_t len)
 {
    u32 chacha_state[CHACHA_STATE_WORDS];
@@ -860,6 +985,14 @@ void add_device_randomness(const void *buf, size_t len)
    _mix_pool_bytes(&entropy, sizeof(entropy));
    _mix_pool_bytes(buf, len);
    spin_unlock_irqrestore(&input_pool.lock, flags);
+
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+	if (crng_init == CRNG_EMPTY && len) {
+		spin_lock_irqsave(&base_crng.lock, flags);
+		extract_entropy(base_crng.key, sizeof(base_crng.key));
+		spin_unlock_irqrestore(&base_crng.lock, flags);
+	}
+#endif
 }
 EXPORT_SYMBOL(add_device_randomness);
@@ -870,7 +1003,17 @@ EXPORT_SYMBOL(add_device_randomness);
  */
 void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy)
 {
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+	unsigned long flags;
+#endif
    mix_pool_bytes(buf, len);
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+	if (crng_init == CRNG_EMPTY) {
+		spin_lock_irqsave(&base_crng.lock, flags);
+		extract_entropy(base_crng.key, sizeof(base_crng.key));
+		spin_unlock_irqrestore(&base_crng.lock, flags);
+	}
+#endif
    credit_init_bits(entropy);
/*
@@ -965,6 +1108,9 @@ static void mix_interrupt_randomness(struct timer_list *work)
     */
    unsigned long pool[2];
    unsigned int count;
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+	unsigned long flags;
+#endif
/* Check to see if we're running on the wrong CPU due to hotplug. */
    local_irq_disable();
@@ -984,6 +1130,13 @@ static void mix_interrupt_randomness(struct timer_list *work)
    local_irq_enable();
mix_pool_bytes(pool, sizeof(pool));
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+	if (crng_init == CRNG_EMPTY) {
+		spin_lock_irqsave(&base_crng.lock, flags);
+		extract_entropy(base_crng.key, sizeof(base_crng.key));
+		spin_unlock_irqrestore(&base_crng.lock, flags);
+	}
+#endif
    credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8));
memzero_explicit(pool, sizeof(pool));
@@ -1090,8 +1243,16 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned int nu
     */
    if (in_irq())
    	this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1;
-	else
+	else {
+#ifdef CONFIG_RTOS_FIX_RANDOM_PERFORMANCE
+		if (crng_init == CRNG_EMPTY) {
+			spin_lock_irqsave(&base_crng.lock, flags);
+			extract_entropy(base_crng.key, sizeof(base_crng.key));
+			spin_unlock_irqrestore(&base_crng.lock, flags);
+		}
+#endif
    	_credit_init_bits(bits);
+	}
 }
void add_input_randomness(unsigned int type, unsigned int code, unsigned int value)
-- 
2.34.1


    

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[PATCH OLK-5.10 1/2] random: Workaround for performance degrade