| Message ID | 1430394211-25209-2-git-send-email-borntraeger@de.ibm.com |
|---|---|
| State | New, archived |
| Headers | show |
On 30/04/2015 13:43, Christian Borntraeger wrote: > +/* must be called with irqs disabled */ > +static inline void __kvm_guest_enter(void) > { > - unsigned long flags; > - > - BUG_ON(preemptible()); Please keep the BUG_ON() in kvm_guest_enter. Otherwise looks good, thanks! Paolo > - local_irq_save(flags); > guest_enter(); > - local_irq_restore(flags); > - > /* KVM does not hold any references to rcu protected data when it > * switches CPU into a guest mode. In fact switching to a guest mode > * is very similar to exiting to userspace from rcu point of view. In > @@ -769,12 +763,27 @@ static inline void kvm_guest_enter(void) > rcu_virt_note_context_switch(smp_processor_id()); > } > > +/* must be called with irqs disabled */ > +static inline void __kvm_guest_exit(void) > +{ > + guest_exit(); > +} > + > +static inline void kvm_guest_enter(void) > +{ > + unsigned long flags; > + > + local_irq_save(flags); > + __kvm_guest_enter(); > + local_irq_restore(flags); > +} > + -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Am 30.04.2015 um 13:50 schrieb Paolo Bonzini: > > > On 30/04/2015 13:43, Christian Borntraeger wrote: >> +/* must be called with irqs disabled */ >> +static inline void __kvm_guest_enter(void) >> { >> - unsigned long flags; >> - >> - BUG_ON(preemptible()); > > Please keep the BUG_ON() in kvm_guest_enter. Otherwise looks good, thanks! would be BUG_ON(!irqs_disabled()) then? -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Am 30.04.2015 um 14:01 schrieb Christian Borntraeger: > Am 30.04.2015 um 13:50 schrieb Paolo Bonzini: >> >> >> On 30/04/2015 13:43, Christian Borntraeger wrote: >>> +/* must be called with irqs disabled */ >>> +static inline void __kvm_guest_enter(void) >>> { >>> - unsigned long flags; >>> - >>> - BUG_ON(preemptible()); >> >> Please keep the BUG_ON() in kvm_guest_enter. Otherwise looks good, thanks! Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Am 30.04.2015 um 14:02 schrieb Christian Borntraeger: > Am 30.04.2015 um 14:01 schrieb Christian Borntraeger: >> Am 30.04.2015 um 13:50 schrieb Paolo Bonzini: >>> >>> >>> On 30/04/2015 13:43, Christian Borntraeger wrote: >>>> +/* must be called with irqs disabled */ >>>> +static inline void __kvm_guest_enter(void) >>>> { >>>> - unsigned long flags; >>>> - >>>> - BUG_ON(preemptible()); >>> >>> Please keep the BUG_ON() in kvm_guest_enter. Otherwise looks good, thanks! > > Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense. Hmmm, too quick. the BUG_ON was there to make sure that rcu_virt_note_context_switch is safe. The reworked code pulls the rcu_virt_note_context_switch within the irq_save section so we no longer need this BUG_ON, no? Christian -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 30/04/2015 14:07, Christian Borntraeger wrote: >>>>> >>>> +static inline void __kvm_guest_enter(void) >>>>> >>>> { >>>>> >>>> - unsigned long flags; >>>>> >>>> - >>>>> >>>> - BUG_ON(preemptible()); >>>> >>> >>>> >>> Please keep the BUG_ON() in kvm_guest_enter. Otherwise looks good, thanks! >> > >> > Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense. > Hmmm, too quick. > the BUG_ON was there to make sure that rcu_virt_note_context_switch is safe. > The reworked code pulls the rcu_virt_note_context_switch within the irq_save > section so we no longer need this BUG_ON, no? Right. I can apply the patches then! Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" 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/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 46f37df..c25d4e5 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2010,12 +2010,14 @@ static int __vcpu_run(struct kvm_vcpu *vcpu) * As PF_VCPU will be used in fault handler, between * guest_enter and guest_exit should be no uaccess. */ - preempt_disable(); - kvm_guest_enter(); - preempt_enable(); + local_irq_disable(); + __kvm_guest_enter(); + local_irq_enable(); exit_reason = sie64a(vcpu->arch.sie_block, vcpu->run->s.regs.gprs); - kvm_guest_exit(); + local_irq_disable(); + __kvm_guest_exit(); + local_irq_enable(); vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); rc = vcpu_post_run(vcpu, exit_reason); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d12b210..2d3b3ce 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -749,16 +749,10 @@ static inline void kvm_iommu_unmap_pages(struct kvm *kvm, } #endif -static inline void kvm_guest_enter(void) +/* must be called with irqs disabled */ +static inline void __kvm_guest_enter(void) { - unsigned long flags; - - BUG_ON(preemptible()); - - local_irq_save(flags); guest_enter(); - local_irq_restore(flags); - /* KVM does not hold any references to rcu protected data when it * switches CPU into a guest mode. In fact switching to a guest mode * is very similar to exiting to userspace from rcu point of view. In @@ -769,12 +763,27 @@ static inline void kvm_guest_enter(void) rcu_virt_note_context_switch(smp_processor_id()); } +/* must be called with irqs disabled */ +static inline void __kvm_guest_exit(void) +{ + guest_exit(); +} + +static inline void kvm_guest_enter(void) +{ + unsigned long flags; + + local_irq_save(flags); + __kvm_guest_enter(); + local_irq_restore(flags); +} + static inline void kvm_guest_exit(void) { unsigned long flags; local_irq_save(flags); - guest_exit(); + __kvm_guest_exit(); local_irq_restore(flags); }
Several kvm architectures disable interrupts before kvm_guest_enter. kvm_guest_enter then uses local_irq_save/restore to disable interrupts again or for the first time. Lets provide underscore versions of kvm_guest_{enter|exit} that assume being called locked. kvm_guest_enter now disables interrupts for the full function and thus we can remove the check for preemptible. This patch then adopts s390/kvm to use local_irq_disable/enable calls which are slighty cheaper that local_irq_save/restore and call these new functions. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> --- arch/s390/kvm/kvm-s390.c | 10 ++++++---- include/linux/kvm_host.h | 27 ++++++++++++++++++--------- 2 files changed, 24 insertions(+), 13 deletions(-)