| Message ID | 20250305011127.4079670-1-dmukhin@ford.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] xen/console: make console buffer size configurable | expand |
On 05.03.2025 02:12, dmkhn@proton.me wrote: > --- a/docs/misc/xen-command-line.pandoc > +++ b/docs/misc/xen-command-line.pandoc > @@ -425,10 +425,13 @@ The following are examples of correct specifications: > ### conring_size > > `= <size>` > > -> Default: `conring_size=16k` > +> Default: `conring_size=32k` > > Specify the size of the console ring buffer. > > +The console ring buffer size can be selected at build time via > +CONFIG_CONRING_SHIFT. And hence, if a value other than 32 is used there, the default above is going to be wrong. IOW it is only the compile time default which is 32k. The run-time default (which is what matters in Default: above) is itself configurable, and hence wants documenting that way. > --- a/xen/drivers/char/Kconfig > +++ b/xen/drivers/char/Kconfig > @@ -96,6 +96,33 @@ config SERIAL_TX_BUFSIZE > > Default value is 32768 (32KiB). > > +config CONRING_SHIFT > + int "Console buffer size (power of 2)" Would you mind adding the word "ring" here? > + range 14 27 > + 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 overridden via 'conring_size=' boot parameter. > + > + Default value is 15 (32KiB). > + > + Examples: > + 27 => 128 MiB > + 26 => 64 MiB > + 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 I don't think an exhaustive list is necessary here. This way it's not really a set of examples, but an enumeration of all possible values. > --- a/xen/drivers/char/console.c > +++ b/xen/drivers/char/console.c > @@ -101,12 +101,12 @@ 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: override build-time CONFIG_CONRING_SHIFT setting. */ > static uint32_t __initdata opt_conring_size; > size_param("conring_size", opt_conring_size); > > -#define _CONRING_SIZE 16384 > -#define CONRING_IDX_MASK(i) ((i)&(conring_size-1)) > +#define _CONRING_SIZE (1UL << CONFIG_CONRING_SHIFT) Imo this ought to be 1U only, seeing ... > +#define CONRING_IDX_MASK(i) ((i) & (conring_size - 1)) > static char __initdata _conring[_CONRING_SIZE]; > static char *__read_mostly conring = _conring; > static uint32_t __read_mostly conring_size = _CONRING_SIZE; ... this use of the constant. Jan
On Wednesday, March 5th, 2025 at 8:42 AM, Jan Beulich <jbeulich@suse.com> wrote: > > > On 05.03.2025 02:12, dmkhn@proton.me wrote: > > > --- a/docs/misc/xen-command-line.pandoc > > +++ b/docs/misc/xen-command-line.pandoc > > @@ -425,10 +425,13 @@ The following are examples of correct specifications: > > ### conring_size > > > > > `= <size>` > > > > -> Default: `conring_size=16k` > > +> Default: `conring_size=32k` > > > > Specify the size of the console ring buffer. > > > > +The console ring buffer size can be selected at build time via > > +CONFIG_CONRING_SHIFT. > > > And hence, if a value other than 32 is used there, the default above is > going to be wrong. IOW it is only the compile time default which is 32k. > The run-time default (which is what matters in Default: above) is itself > configurable, and hence wants documenting that way. > > > --- a/xen/drivers/char/Kconfig > > +++ b/xen/drivers/char/Kconfig > > @@ -96,6 +96,33 @@ config SERIAL_TX_BUFSIZE > > > > Default value is 32768 (32KiB). > > > > +config CONRING_SHIFT > > + int "Console buffer size (power of 2)" > > > Would you mind adding the word "ring" here? > > > + range 14 27 > > + 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 overridden via 'conring_size=' boot parameter. > > + > > + Default value is 15 (32KiB). > > + > > + Examples: > > + 27 => 128 MiB > > + 26 => 64 MiB > > + 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 > > > I don't think an exhaustive list is necessary here. This way it's not really > a set of examples, but an enumeration of all possible values. I decided to keep the exhaustive list so it is a bit easier to do setting selection. > > > --- a/xen/drivers/char/console.c > > +++ b/xen/drivers/char/console.c > > @@ -101,12 +101,12 @@ 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: override build-time CONFIG_CONRING_SHIFT setting. */ > > static uint32_t __initdata opt_conring_size; > > size_param("conring_size", opt_conring_size); > > > > -#define _CONRING_SIZE 16384 > > -#define CONRING_IDX_MASK(i) ((i)&(conring_size-1)) > > +#define _CONRING_SIZE (1UL << CONFIG_CONRING_SHIFT) > > > Imo this ought to be 1U only, seeing ... > > > +#define CONRING_IDX_MASK(i) ((i) & (conring_size - 1)) > > static char __initdata _conring[_CONRING_SIZE]; > > static char *__read_mostly conring = _conring; > > static uint32_t __read_mostly conring_size = _CONRING_SIZE; > > > ... this use of the constant. > > Jan
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index 0c6225391d..1e12d2c6b5 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -425,10 +425,13 @@ The following are examples of correct specifications: ### conring_size > `= <size>` -> Default: `conring_size=16k` +> Default: `conring_size=32k` Specify the size of the console ring buffer. +The console ring buffer size can be selected at build time via +CONFIG_CONRING_SHIFT. + ### console > `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | ehci | xhci | none ]` diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig index e6e12bb413..d3ddb7d87a 100644 --- a/xen/drivers/char/Kconfig +++ b/xen/drivers/char/Kconfig @@ -96,6 +96,33 @@ config SERIAL_TX_BUFSIZE Default value is 32768 (32KiB). +config CONRING_SHIFT + int "Console buffer size (power of 2)" + range 14 27 + 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 overridden via 'conring_size=' boot parameter. + + Default value is 15 (32KiB). + + Examples: + 27 => 128 MiB + 26 => 64 MiB + 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 a84932e384..65468109ba 100644 --- a/xen/drivers/char/console.c +++ b/xen/drivers/char/console.c @@ -101,12 +101,12 @@ 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: override build-time CONFIG_CONRING_SHIFT setting. */ static uint32_t __initdata opt_conring_size; size_param("conring_size", opt_conring_size); -#define _CONRING_SIZE 16384 -#define CONRING_IDX_MASK(i) ((i)&(conring_size-1)) +#define _CONRING_SIZE (1UL << CONFIG_CONRING_SHIFT) +#define CONRING_IDX_MASK(i) ((i) & (conring_size - 1)) static char __initdata _conring[_CONRING_SIZE]; static char *__read_mostly conring = _conring; static uint32_t __read_mostly conring_size = _CONRING_SIZE;
Add new CONRING_SHIFT Kconfig parameter to specify the boot console buffer size as a power of 2. The supported range is [14..27] -> [16KiB..128MiB]. Set default to 15 (32 KiB). Link: https://gitlab.com/xen-project/xen/-/issues/185 Signed-off-by: Denis Mukhin <dmukhin@ford.com> --- Changes v1->v2: - Switched to using powers of 2 in new Kconfig knob --- docs/misc/xen-command-line.pandoc | 5 ++++- xen/drivers/char/Kconfig | 27 +++++++++++++++++++++++++++ xen/drivers/char/console.c | 6 +++--- 3 files changed, 34 insertions(+), 4 deletions(-)