Messages in this thread Patch in this message | | | Date | Mon, 24 Jan 2022 11:03:06 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH v2 5/5] sched: User Mode Concurency Groups |
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On Fri, Jan 21, 2022 at 04:57:29PM +0000, Mark Rutland wrote:
> > @@ -221,8 +227,11 @@ static inline void local_irq_disable_exi > > */ > > static inline void irqentry_irq_enable(struct pt_regs *regs) > > { > > - if (!regs_irqs_disabled(regs)) > > + if (!regs_irqs_disabled(regs)) { > > local_irq_enable(); > > + if (user_mode(regs) && (current->flags & PF_UMCG_WORKER)) > > + umcg_sys_enter(regs, -1); > > + } > > } > > Perhaps it would make sense to have separate umcg_sys_enter(regs) and > umcg_sys_enter_syscall(regs, syscallno)? Even if the former is just a wrapper, > to make the entry/exit bits clearly correspond for all the !syscall cases?
Can do I suppose.
> Also, is the syscall case meant to nest within this, or syscall entry paths not > supposed to call irqentry_irq_enable() ?
No nesting, syscall_ vs irqentry_. And you can't have a syscall and an exception both be from user at the same time :-)
> > /** > > @@ -232,8 +241,11 @@ static inline void irqentry_irq_enable(s > > */ > > static inline void irqentry_irq_disable(struct pt_regs *regs) > > { > > - if (!regs_irqs_disabled(regs)) > > + if (!regs_irqs_disabled(regs)) { > > + if (user_mode(regs) && (current->flags & PF_UMCG_WORKER)) > > + umcg_sys_exit(regs); > > local_irq_disable(); > > + } > > } > > Do the umcg_sys_{enter,exit}() calls need to happen with IRQs unmasked?
Yes; both can end up blocking.
> * If not (and this nests): for arm64 these can live in our > enter_from_user_mode() and exit_to_user_mode() helpers. > > * If so (or this doesn't nest): for arm64 we'd need to rework our > local_daif_{inherit,restore,mask}() calls to handle this, though I've been > meaning to do that anyway to handle pseudo-NMI better. > > Either way, it looks like we'd need helpers along the lines of: > > | static __always_inline void umcg_enter_from_user(struct pt_regs *regs) > | { > | if (current->flags & PF_UMCG_WORKER) > | umcg_sys_enter(regs, -1); > | } > | > | static __always_inline void umcg_exit_to_user(struct pt_regs *regs) > | { > | if (current->flags & PF_UMCG_WORKER) > | umcg_sys_exit(regs); > | }
Would something like:
#ifndef arch_irqentry_irq_enter static __always_inline bool arch_irqentry_irq_enter(struct pt_regs *regs) { if (!regs_irqs_disabled(regs)) { local_irq_enable(); return true; } return false; } #endif
static __always_inline void irqentry_irq_enter(struct pt_regs *regs) { if (arch_irqentry_irq_inherit(regs)) { if (user_mode(regs) && (current->flags & PF_UMCG_WORKER)) umcg_sys_enter(regs, -1); } }
Work? Then arm64 can do:
static __always_inline bool arch_irqentry_irq_enter(struct pt_regs *regs) { local_daif_inherit(); return interrupts_enabled(regs); }
or somesuch...
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