| Message ID | 1423167832-17609-5-git-send-email-riel@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Feb 05, 2015 at 03:23:51PM -0500, riel@redhat.com wrote: > From: Rik van Riel <riel@redhat.com> > > 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@redhat.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > include/linux/context_tracking.h | 8 +++++++- > include/linux/context_tracking_state.h | 1 + > include/linux/kvm_host.h | 3 ++- > 3 files changed, 10 insertions(+), 2 deletions(-) > > 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); > } > > static inline void guest_exit(void) > @@ -86,6 +89,9 @@ static inline void guest_exit(void) > vtime_guest_exit(current); > else > current->flags &= ~PF_VCPU; > + > + if (context_tracking_is_enabled()) > + context_tracking_user_exit(IN_GUEST); > } > > #else > diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h > index 97a81225d037..f3ef027af749 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 { > IN_KERNEL = 0, > IN_USER, > + IN_GUEST, > } state; > }; > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 26f106022c88..c7828a6a9614 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -772,7 +772,8 @@ 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) > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Feb 05, 2015 at 03:23:51PM -0500, riel@redhat.com wrote: > From: Rik van Riel <riel@redhat.com> > > 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@redhat.com> > --- > include/linux/context_tracking.h | 8 +++++++- > include/linux/context_tracking_state.h | 1 + > include/linux/kvm_host.h | 3 ++- > 3 files changed, 10 insertions(+), 2 deletions(-) > > 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); So you should probably just call rcu_user_enter() directly from there. context_tracking_user_enter() is really about userspace boundaries. > } > > static inline void guest_exit(void) > @@ -86,6 +89,9 @@ static inline void guest_exit(void) > vtime_guest_exit(current); > else > current->flags &= ~PF_VCPU; > + > + if (context_tracking_is_enabled()) > + context_tracking_user_exit(IN_GUEST); > } > > #else > diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h > index 97a81225d037..f3ef027af749 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 { > IN_KERNEL = 0, > IN_USER, > + IN_GUEST, > } state; > }; > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 26f106022c88..c7828a6a9614 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -772,7 +772,8 @@ 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()); Should we have a specific CONFIG for this feature? Or relying on full dynticks to be enabled (and thus context tracking enabled) is enough? Thanks. > } > > static inline void kvm_guest_exit(void) > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Feb 05, 2015 at 03:23:51PM -0500, riel@redhat.com wrote: > From: Rik van Riel <riel@redhat.com> > > 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@redhat.com> > --- > include/linux/context_tracking.h | 8 +++++++- > include/linux/context_tracking_state.h | 1 + > include/linux/kvm_host.h | 3 ++- > 3 files changed, 10 insertions(+), 2 deletions(-) > > 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) That's nitpicking but != IN_KERNEL would be more generic. We are exiting an exception and we know that the exception executes IN_KERNEL, so we want to restore any context (whether IN_USER, IN_GUEST, or anything added in the future) prior the exception if that was anything else than IN_KERNEL. > 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); > } > > static inline void guest_exit(void) > @@ -86,6 +89,9 @@ static inline void guest_exit(void) > vtime_guest_exit(current); > else > current->flags &= ~PF_VCPU; > + > + if (context_tracking_is_enabled()) > + context_tracking_user_exit(IN_GUEST); I suggest you to restore RCU before anything else. I believe cputime accounting doesn't use RCU but we never know with all the debug/tracing code behind, the acct accounting... Thanks. > } > > #else > diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h > index 97a81225d037..f3ef027af749 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 { > IN_KERNEL = 0, > IN_USER, > + IN_GUEST, > } state; > }; > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 26f106022c88..c7828a6a9614 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -772,7 +772,8 @@ 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) > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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); } static inline void guest_exit(void) @@ -86,6 +89,9 @@ static inline void guest_exit(void) vtime_guest_exit(current); else current->flags &= ~PF_VCPU; + + if (context_tracking_is_enabled()) + context_tracking_user_exit(IN_GUEST); } #else diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h index 97a81225d037..f3ef027af749 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 { IN_KERNEL = 0, IN_USER, + IN_GUEST, } state; }; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 26f106022c88..c7828a6a9614 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -772,7 +772,8 @@ 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)