2 files changed, 24 insertions, 1 deletions

diff --git a/init/Kconfig b/init/Kconfig
index bccc1d607be5..a9c4aefd5436 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -862,6 +862,28 @@ config LOG_CPU_MAX_BUF_SHIFT
                      13 =>   8 KB for each CPU
                      12 =>   4 KB for each CPU
 
+config NMI_LOG_BUF_SHIFT
+        int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
+        range 10 21
+        default 13
+        depends on PRINTK_NMI
+        help
+          Select the size of a per-CPU buffer where NMI messages are temporary
+          stored. They are copied to the main log buffer in a safe context
+          to avoid a deadlock. The value defines the size as a power of 2.
+
+          NMI messages are rare and limited. The largest one is when
+          a backtrace is printed. It usually fits into 4KB. Select
+          8KB if you want to be on the safe side.
+
+          Examples:
+                     17 => 128 KB for each CPU
+                     16 =>  64 KB for each CPU
+                     15 =>  32 KB for each CPU
+                     14 =>  16 KB for each CPU
+                     13 =>   8 KB for each CPU
+                     12 =>   4 KB for each CPU
+
 #
 # Architectures with an unreliable sched_clock() should select this:
 #
diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
index 572f94922230..bf08557d7e3d 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -41,7 +41,8 @@ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
 static int printk_nmi_irq_ready;
 atomic_t nmi_message_lost;
 
-#define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
+#define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) -              \
+                         sizeof(atomic_t) - sizeof(struct irq_work))
 
 struct nmi_seq_buf {
         atomic_t                len;    /* length of written data */