Messages in this thread | | | Date | Tue, 27 Jul 2021 11:52:09 -0300 | From | Marcelo Tosatti <> | Subject | Re: [patch 1/4] add basic task isolation prctl interface |
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On Tue, Jul 27, 2021 at 03:09:30PM +0200, Frederic Weisbecker wrote: > On Tue, Jul 27, 2021 at 02:38:15PM +0200, nsaenzju@redhat.com wrote: > > Hi Marcelo, > > > > On Tue, 2021-07-27 at 08:00 -0300, Marcelo Tosatti wrote: > > OK, sorry if I'm being thick, but what is the benefit of having a distincnt > > PR_ISOL_MODE instead expressing everything as PR_ISOL_FEATURES. > > > > PR_ISOL_MODE_NONE == Empty PR_ISOL_FEATURES bitmap > > > > PR_ISOL_MODE_NORMAL == Bitmap of commonly used PR_ISOL_FEATURES > > (we could introduce a define) > > > > PR_ISOL_MODE_NORMAL+PR_ISOL_VSYSCALLS == Custom bitmap > > > > Other than that, my rationale is that if you extend PR_ISOL_MODE_NORMAL's > > behaviour as new features are merged, wouldn't you be potentially breaking > > userspace (i.e. older applications might not like the new default)? > > I agree with Nicolas, and that was Thomas request too. > Let's leave policy implementation to userspace and take > only the individual isolation features to the kernel. > > CPU/Task isolation is a relatively young feature and many users don't > communicate much about their needs. We don't know exactly how finegrained > the ABI will need to be so let's not make too many high level assumptions. > > It's easy for userspace to set all isolation bits by itself. > > Besides, those bits will be implemented one by one over time, this > means that a prctl() bit saying "isolate everything" will have a different > behaviour as those features get integrated. And we really want well defined > behaviours. > > Thanks. > >
OK, how about this:
...
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.
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) ...
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