| Message ID | 20190305103002.5801-3-borntraeger@de.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | disabling halt polling for nested virtualization | expand |
On Tue, 5 Mar 2019 05:30:02 -0500 Christian Borntraeger <borntraeger@de.ibm.com> wrote: > We do track the current steal time of the host CPUs. Let us use > this value to disable halt polling if the steal time goes beyond > a predefined value. (12.5% for now). Might make sense to make it tweakable. On the other hand, a reasonable value might be good enough :) > > Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> > --- > arch/s390/include/asm/kvm_host.h | 6 ++++++ > arch/s390/kvm/Kconfig | 1 + > 2 files changed, 7 insertions(+) > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index a4962761e1dd..f699983a8d09 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -884,6 +884,12 @@ struct kvm_arch_async_pf { > unsigned long pfault_token; > }; > > +static inline bool kvm_arch_no_poll(void) > +{ > + /* do not poll with more than 12.5% steal */ > + return S390_lowcore.avg_steal_timer > (TICK_USEC << 12) / 8; That's an average anyway, correct? > +} > + > bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu); > > void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, > diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig > index 767453faacfc..e987e73738b5 100644 > --- a/arch/s390/kvm/Kconfig > +++ b/arch/s390/kvm/Kconfig > @@ -31,6 +31,7 @@ config KVM > select HAVE_KVM_IRQFD > select HAVE_KVM_IRQ_ROUTING > select HAVE_KVM_INVALID_WAKEUPS > + select HAVE_KVM_NO_POLL > select SRCU > select KVM_VFIO > ---help---
Hi Christian,
I love your patch! Yet something to improve:
[auto build test ERROR on kvm/linux-next]
[also build test ERROR on v5.0 next-20190305]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Christian-Borntraeger/KVM-polling-add-architecture-backend-to-disable-polling/20190305-193431
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: s390-allyesconfig (attached as .config)
compiler: s390x-linux-gnu-gcc (Debian 8.2.0-11) 8.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=8.2.0 make.cross ARCH=s390
All errors (new ones prefixed by >>):
In file included from include/linux/kvm_host.h:38,
from arch/s390/kernel/asm-offsets.c:11:
arch/s390/include/asm/kvm_host.h: In function 'kvm_arch_no_poll':
>> arch/s390/include/asm/kvm_host.h:887:22: error: 'struct lowcore' has no member named 'avg_steal_timer'; did you mean 'steal_timer'?
return S390_lowcore.avg_steal_timer > (TICK_USEC << 12) / 8;
^~~~~~~~~~~~~~~
steal_timer
make[2]: *** [arch/s390/kernel/asm-offsets.s] Error 1
make[2]: Target '__build' not remade because of errors.
make[1]: *** [prepare0] Error 2
make[1]: Target 'prepare' not remade because of errors.
make: *** [sub-make] Error 2
vim +887 arch/s390/include/asm/kvm_host.h
883
884 static inline bool kvm_arch_no_poll(void)
885 {
886 /* do not poll with more than 12.5% steal */
> 887 return S390_lowcore.avg_steal_timer > (TICK_USEC << 12) / 8;
888 }
889
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index a4962761e1dd..f699983a8d09 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -884,6 +884,12 @@ struct kvm_arch_async_pf { unsigned long pfault_token; }; +static inline bool kvm_arch_no_poll(void) +{ + /* do not poll with more than 12.5% steal */ + return S390_lowcore.avg_steal_timer > (TICK_USEC << 12) / 8; +} + bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu); void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig index 767453faacfc..e987e73738b5 100644 --- a/arch/s390/kvm/Kconfig +++ b/arch/s390/kvm/Kconfig @@ -31,6 +31,7 @@ config KVM select HAVE_KVM_IRQFD select HAVE_KVM_IRQ_ROUTING select HAVE_KVM_INVALID_WAKEUPS + select HAVE_KVM_NO_POLL select SRCU select KVM_VFIO ---help---
We do track the current steal time of the host CPUs. Let us use this value to disable halt polling if the steal time goes beyond a predefined value. (12.5% for now). Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> --- arch/s390/include/asm/kvm_host.h | 6 ++++++ arch/s390/kvm/Kconfig | 1 + 2 files changed, 7 insertions(+)