From 126a6a542446f1a49b9f3c69237c87df3eb4e6e1 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Tue, 10 Feb 2015 15:27:54 -0500 Subject: [PATCH] kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest The host kernel is not doing anything while the CPU is executing a KVM guest VCPU, so it can be marked as being in an extended quiescent state, identical to that used when running user space code. The only exception to that rule is when the host handles an interrupt, which is already handled by the irq code, which calls rcu_irq_enter and rcu_irq_exit. The guest_enter and guest_exit functions already switch vtime accounting independent of context tracking. Leave those calls where they are, instead of moving them into the context tracking code. Reviewed-by: Paul E. McKenney Signed-off-by: Rik van Riel Cc: Paul E. McKenney Cc: Andy Lutomirski Cc: Will deacon Cc: Marcelo Tosatti Cc: Christian Borntraeger Cc: Luiz Capitulino Cc: Paolo Bonzini Signed-off-by: Frederic Weisbecker --- include/linux/context_tracking.h | 6 ++++++ include/linux/context_tracking_state.h | 1 + include/linux/kvm_host.h | 3 ++- 3 files changed, 9 insertions(+), 1 deletion(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 7f1810a3b5a4..2821838256b4 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -81,10 +81,16 @@ static inline void guest_enter(void) vtime_guest_enter(current); else current->flags |= PF_VCPU; + + if (context_tracking_is_enabled()) + context_tracking_enter(CONTEXT_GUEST); } static inline void guest_exit(void) { + if (context_tracking_is_enabled()) + context_tracking_exit(CONTEXT_GUEST); + if (vtime_accounting_enabled()) vtime_guest_exit(current); else diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h index ad4458588b47..6b7b96a32b75 100644 --- a/include/linux/context_tracking_state.h +++ b/include/linux/context_tracking_state.h @@ -15,6 +15,7 @@ struct context_tracking { enum ctx_state { CONTEXT_KERNEL = 0, CONTEXT_USER, + CONTEXT_GUEST, } state; }; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d12b2104d19b..cc8c61c5459c 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -766,7 +766,8 @@ static inline void kvm_guest_enter(void) * one time slice). Lets treat guest mode as quiescent state, just like * we do with user-mode execution. */ - rcu_virt_note_context_switch(smp_processor_id()); + if (!context_tracking_cpu_is_enabled()) + rcu_virt_note_context_switch(smp_processor_id()); } static inline void kvm_guest_exit(void) -- 2.39.5