linux-kernel - Re: [PATCH v3 39/59] KVM: arm/arm64: GICv4: Add property field and per-VM predicate

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Date:   Sat, 26 Aug 2017 21:49:15 +0200
From:   Christoffer Dall <cdall@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Eric Auger <eric.auger@...hat.com>,
        Shanker Donthineni <shankerd@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v3 39/59] KVM: arm/arm64: GICv4: Add property field and
 per-VM predicate

On Mon, Jul 31, 2017 at 06:26:17PM +0100, Marc Zyngier wrote:
> Add a new has_gicv4 field in the global VGIC state that indicates
> whether the HW is GICv4 capable, as a per-VM predicate indicating
> if there is a possibility for a VM to support direct injection
> (the above being true and the VM having an ITS).
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  include/kvm/arm_vgic.h           | 3 +++
>  virt/kvm/arm/vgic/vgic-mmio-v3.c | 5 +++++
>  virt/kvm/arm/vgic/vgic.h         | 2 ++
>  3 files changed, 10 insertions(+)
> 
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index ee8587c8c715..84694b42373a 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -73,6 +73,9 @@ struct vgic_global {
>  	/* Only needed for the legacy KVM_CREATE_IRQCHIP */
>  	bool			can_emulate_gicv2;
>  
> +	/* Does have GICv4? */

nit: questionable comment, how about

  /* Hardware has GICv4? */
or
  /* Do we have GICv4? */

> +	bool			has_gicv4;
> +
>  	/* GIC system register CPU interface */
>  	struct static_key_false gicv3_cpuif;
>  
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index 714fa3933546..74109ca75cc0 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -54,6 +54,11 @@ bool vgic_has_its(struct kvm *kvm)
>  	return dist->has_its;
>  }
>  
> +bool vgic_is_v4_capable(struct kvm *kvm)
> +{
> +	return kvm_vgic_global_state.has_gicv4 && vgic_has_its(kvm);
> +}
> +

uber nit: the naming here is a bit funny, because we won't be presenting
a GICv4 GIC to the guest, so I'd prefer something like
vgic_supports_direct_msis() or something like that, but this is
obviously not a deal breaker.

>  static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu,
>  					    gpa_t addr, unsigned int len)
>  {
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index 3002b72d938b..90f6436a11aa 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -229,4 +229,6 @@ int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
>  			 u32 devid, u32 eventid, struct vgic_irq **irq);
>  struct vgic_its *vgic_msi_to_its(struct kvm *kvm, struct kvm_msi *msi);
>  
> +bool vgic_is_v4_capable(struct kvm *kvm);
> +
>  #endif
> -- 
> 2.11.0
> 

Thanks,
-Christoffer