Re: [PATCH v4 4/5] KVM: introduce kvm_arch functions for IRQ bypass

From: Alex Williamson <alex.williamson@redhat.com>
To: Eric Auger <eric.auger@linaro.org>
Cc: eric.auger@st.com, feng.wu@intel.com, pbonzini@redhat.com,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	avi.kivity@gmail.com, mtosatti@redhat.com, joro@8bytes.org,
	marc.zyngier@arm.com, christoffer.dall@linaro.org,
	linux-kernel@vger.kernel.org, patches@linaro.org
Subject: Re: [PATCH v4 4/5] KVM: introduce kvm_arch functions for IRQ bypass
Date: Fri, 07 Aug 2015 14:09:14 -0600	[thread overview]
Message-ID: <1438978154.4023.262.camel@redhat.com> (raw)
In-Reply-To: <1438622444-25444-5-git-send-email-eric.auger@linaro.org>

On Mon, 2015-08-03 at 19:20 +0200, Eric Auger wrote:
> This patch introduces
> - kvm_arch_irq_bypass_add_producer
> - kvm_arch_irq_bypass_del_producer
> - kvm_arch_irq_bypass_stop
> - kvm_arch_irq_bypass_start
> 
> They make possible to specialize the KVM IRQ bypass consumer in
> case CONFIG_KVM_HAVE_IRQ_BYPASS is set.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
> Signed-off-by: Feng Wu <feng.wu@intel.com>
> 
> ---
> 
> v2 -> v3 (Feng Wu):
> - use 'kvm_arch_irq_bypass_start' instead of 'kvm_arch_irq_bypass_resume'
> - Remove 'kvm_arch_irq_bypass_update', which is not needed to be
>   a irqbypass callback per Alex's comments.
> - Make kvm_arch_irq_bypass_add_producer return 'int'
> 
> v1 -> v2:
> - use CONFIG_KVM_HAVE_IRQ_BYPASS instead CONFIG_IRQ_BYPASS_MANAGER
> - rename all functions according to Paolo's proposal
> - add kvm_arch_irq_bypass_update according to Feng's need
> ---
>  include/linux/kvm_host.h | 33 +++++++++++++++++++++++++++++++++
>  virt/kvm/Kconfig         |  3 +++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 05e99b8..84b5feb 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -24,6 +24,7 @@
>  #include <linux/err.h>
>  #include <linux/irqflags.h>
>  #include <linux/context_tracking.h>
> +#include <linux/irqbypass.h>
>  #include <asm/signal.h>
>  
>  #include <linux/kvm.h>
> @@ -1151,5 +1152,37 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
>  {
>  }
>  #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
> +
> +#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
> +
> +int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
> +			   struct irq_bypass_producer *);
> +void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *,
> +			   struct irq_bypass_producer *);
> +void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *);
> +void kvm_arch_irq_bypass_start(struct irq_bypass_consumer *);
> +
> +#else

Do we really need static inline stubs?  When would they get used?  How
would they work since we call them via function pointers?

> +
> +static inline int kvm_arch_irq_bypass_add_producer(
> +			struct irq_bypass_consumer *cons,
> +			struct irq_bypass_producer *prod)
> +{
> +	return -1;

No reason not to stick with standard errno values, is there?  -EINVAL
Thanks,

Alex

> +}
> +static inline void kvm_arch_irq_bypass_del_producer(
> +			struct irq_bypass_consumer *cons,
> +			struct irq_bypass_producer *prod)
> +{
> +}
> +static inline void kvm_arch_irq_bypass_stop(
> +			struct irq_bypass_consumer *cons)
> +{
> +}
> +static inline void kvm_arch_irq_bypass_start(
> +			struct irq_bypass_consumer *cons)
> +{
> +}
> +#endif /* CONFIG_HAVE_KVM_IRQ_BYPASS */
>  #endif
>  
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index e2c876d..9f8014d 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -47,3 +47,6 @@ config KVM_GENERIC_DIRTYLOG_READ_PROTECT
>  config KVM_COMPAT
>         def_bool y
>         depends on COMPAT && !S390
> +
> +config HAVE_KVM_IRQ_BYPASS
> +       bool