[PATCH v3 24/27] KVM: arm64: Enable GICv3 common sysreg trapping via command-line

[Christoffer Dall]

On Fri, Jun 09, 2017 at 12:49:53PM +0100, Marc Zyngier wrote:
> Now that we're able to safely handle common sysreg access, let's
> give the user the opportunity to enable it by passing a specific
> command-line option (vgic_v3.common_trap).
> 
> Tested-by: Alexander Graf <agraf at suse.de>
> Acked-by: David Daney <david.daney at cavium.com>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>

Acked-by: Christoffer Dall <cdall at linaro.org>

> ---
>  Documentation/admin-guide/kernel-parameters.txt |  4 ++++
>  include/linux/irqchip/arm-gic-v3.h              |  1 +
>  virt/kvm/arm/vgic/vgic-v3.c                     | 11 ++++++++++-
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 88bdc421351f..aa8341e73b35 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1837,6 +1837,10 @@
>  			[KVM,ARM] Trap guest accesses to GICv3 group-1
>  			system registers
>  
> +	kvm-arm.vgic_v3_common_trap=
> +			[KVM,ARM] Trap guest accesses to GICv3 common
> +			system registers
> +
>  	kvm-intel.ept=	[KVM,Intel] Disable extended page tables
>  			(virtualized MMU) support on capable Intel chips.
>  			Default is 1 (enabled)
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index 46a1e0943cf8..f0cebb6e57d0 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -417,6 +417,7 @@
>  
>  #define ICH_HCR_EN			(1 << 0)
>  #define ICH_HCR_UIE			(1 << 1)
> +#define ICH_HCR_TC			(1 << 10)
>  #define ICH_HCR_TALL0			(1 << 11)
>  #define ICH_HCR_TALL1			(1 << 12)
>  #define ICH_HCR_EOIcount_SHIFT		27
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index ffc581b70c4e..3960e89c05ad 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -23,6 +23,7 @@
>  
>  static bool group0_trap;
>  static bool group1_trap;
> +static bool common_trap;
>  
>  void vgic_v3_set_underflow(struct kvm_vcpu *vcpu)
>  {
> @@ -246,6 +247,8 @@ void vgic_v3_enable(struct kvm_vcpu *vcpu)
>  		vgic_v3->vgic_hcr |= ICH_HCR_TALL0;
>  	if (group1_trap)
>  		vgic_v3->vgic_hcr |= ICH_HCR_TALL1;
> +	if (common_trap)
> +		vgic_v3->vgic_hcr |= ICH_HCR_TC;
>  }
>  
>  int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
> @@ -431,6 +434,12 @@ static int __init early_group1_trap_cfg(char *buf)
>  }
>  early_param("kvm-arm.vgic_v3_group1_trap", early_group1_trap_cfg);
>  
> +static int __init early_common_trap_cfg(char *buf)
> +{
> +	return strtobool(buf, &common_trap);
> +}
> +early_param("kvm-arm.vgic_v3_common_trap", early_common_trap_cfg);
> +
>  /**
>   * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
>   * @node:	pointer to the DT node
> @@ -489,7 +498,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
>  	}
>  #endif
>  
> -	if (group0_trap || group1_trap) {
> +	if (group0_trap || group1_trap || common_trap) {
>  		kvm_info("GICv3 sysreg trapping enabled (reduced performance)\n");
>  		static_branch_enable(&vgic_v3_cpuif_trap);
>  	}
> -- 
> 2.11.0
>