Re: [patch 1/4] add basic task isolation prctl interface

[Frederic Weisbecker <frederic@kernel.org>]

On Tue, Jul 27, 2021 at 11:52:09AM -0300, Marcelo Tosatti wrote:
> The meaning of isolated is specified as follows:
> 
> Isolation features
> ==================
> 
> - prctl(PR_ISOL_GET, ISOL_SUP_FEATURES, 0, 0, 0) returns the supported
> features as a return value.
> 
> - prctl(PR_ISOL_SET, ISOL_FEATURES, bitmask, 0, 0) enables the features in
> the bitmask.
> 
> - prctl(PR_ISOL_GET, ISOL_FEATURES, 0, 0, 0) returns the currently
> enabled features.

So what are the ISOL_FEATURES here? A mode that we enter such as flush
vmstat _everytime_ we resume to userpace after (and including) this prctl() ?

If so I'd rather call that ISOL_MODE because feature is too general.

> 
> The supported features are:
> 
> ISOL_F_QUIESCE_ON_URET: quiesce deferred actions on return to userspace.
> ----------------------
> 
> Quiescing of different actions can be performed on return to userspace.
> 
> - prctl(PR_ISOL_GET, PR_ISOL_SUP_QUIESCE_CFG, 0, 0, 0) returns
> the supported actions to be quiesced.
> 
> - prctl(PR_ISOL_SET, PR_ISOL_QUIESCE_CFG, quiesce_bitmask, 0, 0) returns
> the currently supported actions to be quiesced.
> 
> - prctl(PR_ISOL_GET, PR_ISOL_QUIESCE_CFG, 0, 0, 0) returns
> the currently enabled actions to be quiesced.
> 
> #define ISOL_F_QUIESCE_VMSTAT_SYNC      (1<<0)
> #define ISOL_F_QUIESCE_NOHZ_FULL        (1<<1)
> #define ISOL_F_QUIESCE_DEFER_TLB_FLUSH  (1<<2)

And then PR_ISOL_QUIESCE_CFG is a oneshot operation that applies only upon
return to this ctrl, right? If so perhaps this should be called just
ISOL_QUIESCE or ISOL_QUIESCE_ONCE or ISOL_REQ ?

But that's just naming debate because otherwise that prctl layout looks good
to me.

Thanks!