Am 05.02.2015 um 17:35 schrieb riel@xxxxxxxxxx:
> From: Rik van Riel <riel@xxxxxxxxxx>
>
> 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, so leave those calls
> where they are, instead of moving them into the context tracking
> code.
>
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
> ---
> include/linux/context_tracking.h | 8 +++++++-
> include/linux/context_tracking_state.h | 1 +
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> index bd9f000fc98d..a5d3bb44b897 100644
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -43,7 +43,7 @@ static inline enum ctx_state exception_enter(void)
> static inline void exception_exit(enum ctx_state prev_ctx)
> {
> if (context_tracking_is_enabled()) {
> - if (prev_ctx == IN_USER)
> + if (prev_ctx == IN_USER || prev_ctx == IN_GUEST)
> context_tracking_user_enter(prev_ctx);
> }
> }
> @@ -78,6 +78,9 @@ static inline void guest_enter(void)
> vtime_guest_enter(current);
> else
> current->flags |= PF_VCPU;
> +
> + if (context_tracking_is_enabled())
> + context_tracking_user_enter(IN_GUEST);
> }
Couldnt we make
rcu_virt_note_context_switch(smp_processor_id());
conditional in include/linux/kvm_host.h (kvm_guest_enter)
e.g. something like
if (!context_tracking_is_enabled())
rcu_virt_note_context_switch(smp_processor_id());
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