Re: [PATCH v3 3/4] xen/console: add build-time rate-limiting controls

On Thu, Jul 16, 2026 at 11:59:34AM +0200, Teddy Astie wrote:
> Le 15/07/2026 à 22:24, [email protected] a écrit :
> > From: Denis Mukhin <[email protected]>
> > 
> > Introduce CONFIG_PRINTK_RATELIMIT_MS and CONFIG_PRINTK_RATELIMIT_BURST
> > for configuring rate-limiting policy at the compile time.
> > 
> > Use symbols for global rate-limiting initialization in the console driver.
> > 
> > Signed-off-by: Denis Mukhin <[email protected]>
> > ---
> > Changes since v2:
> > - moved rate-limiting controls to common/Kconfig
> > ---
> >   xen/common/Kconfig         | 29 +++++++++++++++++++++++++++++
> >   xen/drivers/char/console.c |  6 ++++--
> >   2 files changed, 33 insertions(+), 2 deletions(-)
> > 
> > diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> > index da80fdba8469..fd22806884e0 100644
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -672,4 +672,33 @@ config PM_STATS
> >   	  Enable collection of performance management statistics to aid in
> >   	  analyzing and tuning power/performance characteristics of the system
> > +menu "Console rate-limiting"
> > +
> > +config PRINTK_RATELIMIT_MS
> > +	int "printk rate-limiting time window (milliseconds)"
> > +	default 5000
> > +	help
> > +	  Specifies the time window, in milliseconds, for rate-limited printk
> > +	  messages. No more than `CONFIG_PRINTK_RATELIMIT_BURST` messages will be
> > +	  printed within this window.
> > +
> > +	  Setting this value to 0 disables rate-limiting entirely.
> > +
> > +	  Rate-limited messages are those controlled by the `loglvl` and
> > +	  `guest_loglvl` command-line parameters.
> > +
> > +config PRINTK_RATELIMIT_BURST
> > +	int "printk rate-limited message burst size"
> > +	default 10
> > +	help
> > +	  Defines the maximum number of rate-limited printk messages that may be
> > +	  printed within each `CONFIG_PRINTK_RATELIMIT_MS` time window.
> > +
> > +	  Setting this value to 0 disables rate-limiting entirely.
> > +
> > +	  Rate-limited messages are those controlled by the `loglvl` and
> > +	  `guest_loglvl` command-line parameters.
> > +
> > +endmenu
> > +
> >   endmenu
> 
> Given that setting 0 to either will disable rate limiting, would it be
> preferable instead to have a more general PRINTK_RATELIMIT toggle, where :
> 
> Setting it to true would enable configuration of ms and burst (rejecting 0
> if possible).
> Setting it to false would set both to 0 hence disabling rate limiting by
> default.
> 
> And we do something like
> 
> static const unsigned int printk_ratelimit_ms =
>   IS_ENABLED(CONFIG_PRINTK_RATELIMIT) ? CONFIG_PRINTK_RATELIMIT_MS : 0;
> 
> (similarly for burst)
> 
> ?

I can hide both selectors behind CONFIG_PRINTK_RATELIMIT.