Messages in this thread Patch in this message | | | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH 1/5] entry: Pass pt_regs to irqentry_exit_cond_resched() | Date | Wed, 10 Aug 2022 09:25:48 +0200 |
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On Wed, Aug 10 2022 at 01:18, Thomas Gleixner wrote: > Both clearly demonstrate how well tested this XEN_PV muck is which means > we should just delete it. > > Anyway. This wants the fix below.
which is not sufficient. If CONFIG_PREEMPT_DYNAMIC is set then CONFIG_PREEMPTION is set too, which makes the preemtible hypercall magic a complete NOP. So if the dynamic call is disabled, then such a several seconds (sic!) hypercall cannot be preempted at all.
Something like the below then. Oh well...
Thanks,
tglx --- --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -253,7 +253,8 @@ SYSCALL_DEFINE0(ni_syscall) } #ifdef CONFIG_XEN_PV -#ifndef CONFIG_PREEMPTION + +#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) /* * Some hypercalls issued by the toolstack can take many 10s of * seconds. Allow tasks running hypercalls via the privcmd driver to @@ -283,9 +284,18 @@ static __always_inline void restore_inhc { __this_cpu_write(xen_in_preemptible_hcall, inhcall); } + +static __always_inline void xenpv_irqentry_exit_cond_resched(void) +{ + instrumentation_begin(); + raw_irqentry_exit_cond_resched(); + trace_hardirqs_on(); + instrumentation_end(); +} #else static __always_inline bool get_and_clear_inhcall(void) { return false; } static __always_inline void restore_inhcall(bool inhcall) { } +static __always_inline void xenpv_irqentry_exit_cond_resched(void) { } #endif static void __xen_pv_evtchn_do_upcall(struct pt_regs *regs) @@ -306,11 +316,11 @@ static void __xen_pv_evtchn_do_upcall(st instrumentation_begin(); run_sysvec_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs); + instrumentation_end(); inhcall = get_and_clear_inhcall(); if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) { - irqentry_exit_cond_resched(); - instrumentation_end(); + xenpv_irqentry_exit_cond_resched(); restore_inhcall(inhcall); } else { instrumentation_end(); --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -416,6 +416,7 @@ irqentry_state_t noinstr irqentry_enter( * Conditional reschedule with additional sanity checks. */ void raw_irqentry_exit_cond_resched(void); + #ifdef CONFIG_PREEMPT_DYNAMIC #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) #define irqentry_exit_cond_resched_dynamic_enabled raw_irqentry_exit_cond_resched --- a/include/xen/xen-ops.h +++ b/include/xen/xen-ops.h @@ -194,7 +194,7 @@ bool xen_running_on_version_or_later(uns void xen_efi_runtime_setup(void); -#if defined(CONFIG_XEN_PV) && !defined(CONFIG_PREEMPTION) +#if defined(CONFIG_XEN_PV) && (!defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)) DECLARE_PER_CPU(bool, xen_in_preemptible_hcall); --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -385,6 +385,7 @@ void raw_irqentry_exit_cond_resched(void preempt_schedule_irq(); } } + #ifdef CONFIG_PREEMPT_DYNAMIC #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
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