[v2,26/35] xen/console: make console buffer size configurable

Commit Message

Denis Mukhin via B4 Relay Dec. 6, 2024, 4:41 a.m. UTC

From: Denis Mukhin <[e-mail]>

Add new CONRING_LOG_SHIFT Kconfig parameter to specify the boot console buffer
size as a power of 2.

Bump default size to 32 KiB.

Link: https://gitlab.com/xen-project/xen/-/issues/185
Signed-off-by: Denis Mukhin <[e-mail]>
---
 xen/drivers/char/Kconfig   | 23 +++++++++++++++++++++++
 xen/drivers/char/console.c |  4 ++--
 2 files changed, 25 insertions(+), 2 deletions(-)

Patch

diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig
index e6e12bb4139717f9319031f51f5d20155d2caee2..3bc892fc38d8cdeb3c76ea44d747f712a8d0d372 100644
--- a/xen/drivers/char/Kconfig
+++ b/xen/drivers/char/Kconfig
@@ -96,6 +96,29 @@  config SERIAL_TX_BUFSIZE
 
 	  Default value is 32768 (32KiB).
 
+config CONRING_LOG_SHIFT
+	int "Console buffer size"
+	range 14 25
+	default 15
+	help
+	  Select the boot console buffer size as a power of 2.
+	  Run-time console buffer size is the same as the boot console size,
+	  unless enforced via 'conring_size=' boot parameter.
+
+	  Examples:
+	    25 =>  32 MiB
+	    24 =>  16 MiB
+	    23 =>   8 MiB
+	    22 =>   4 MiB
+	    21 =>   2 MiB
+	    20 =>   1 MiB
+	    19 => 512 KiB
+	    18 => 256 KiB
+	    17 => 128 KiB
+	    16 =>  64 KiB
+	    15 =>  32 KiB
+	    14 =>  16 KiB
+
 config XHCI
 	bool "XHCI DbC UART driver"
 	depends on X86
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index d22fb4a253af26f9b51d91bd408e1dbf4bb5a7c1..581ee22b85302a54db5b9d5d28e8b2d689d31403 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -104,11 +104,11 @@  static int cf_check parse_console_timestamps(const char *s);
 custom_runtime_param("console_timestamps", parse_console_timestamps,
                      con_timestamp_mode_upd);
 
-/* conring_size: allows a large console ring than default (16kB). */
+/* conring_size: allows a large console ring than default (32 KiB). */
 static uint32_t __initdata opt_conring_size;
 size_param("conring_size", opt_conring_size);
 
-#define _CONRING_SIZE 16384
+#define _CONRING_SIZE       (1U << CONFIG_CONRING_LOG_SHIFT)
 #define CONRING_IDX_MASK(i) ((i)&(conring_size-1))
 static char __initdata _conring[_CONRING_SIZE];
 static char *__read_mostly conring = _conring;