Re: [PATCH v2 04/25] KVM: arm64: vgic-v3: Add hook to handle guest GICv3 sysreg accesses at EL2

[Christoffer Dall <cdall@linaro.org>]

On Thu, Jun 01, 2017 at 11:20:56AM +0100, Marc Zyngier wrote:
> In order to start handling guest access to GICv3 system registers,
> let's add a hook that will get called when we trap a system register
> access. This is gated by a new static key (vgic_v3_cpuif_trap).
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

> ---
>  arch/arm64/include/asm/kvm_hyp.h |  1 +
>  arch/arm64/kvm/hyp/switch.c      | 14 ++++++++++++++
>  include/kvm/arm_vgic.h           |  1 +
>  virt/kvm/arm/hyp/vgic-v3-sr.c    | 38 ++++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/vgic/vgic-v3.c      |  2 ++
>  5 files changed, 56 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index b18e852d27e8..4572a9b560fa 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -127,6 +127,7 @@ int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu);
>  
>  void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
>  void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
> +int __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu);
>  
>  void __timer_save_state(struct kvm_vcpu *vcpu);
>  void __timer_restore_state(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index aede1658aeda..dfd8ca16601b 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -350,6 +350,20 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
>  		}
>  	}
>  
> +	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
> +	    exit_code == ARM_EXCEPTION_TRAP &&
> +	    (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 ||
> +	     kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_CP15_32)) {
> +		int ret = __vgic_v3_perform_cpuif_access(vcpu);
> +
> +		if (ret == 1) {
> +			__skip_instr(vcpu);
> +			goto again;
> +		}
> +
> +		/* 0 falls through to be handled out of EL2 */
> +	}
> +
>  	fp_enabled = __fpsimd_enabled();
>  
>  	__sysreg_save_guest_state(guest_ctxt);
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index ef718586321c..39b9fc4dc65d 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -285,6 +285,7 @@ struct vgic_cpu {
>  };
>  
>  extern struct static_key_false vgic_v2_cpuif_trap;
> +extern struct static_key_false vgic_v3_cpuif_trap;
>  
>  int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
>  void kvm_vgic_early_init(struct kvm *kvm);
> diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
> index 990d9d1e85d0..943bf11252d9 100644
> --- a/virt/kvm/arm/hyp/vgic-v3-sr.c
> +++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
> @@ -19,6 +19,7 @@
>  #include <linux/irqchip/arm-gic-v3.h>
>  #include <linux/kvm_host.h>
>  
> +#include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
>  
>  #define vtr_to_max_lr_idx(v)		((v) & 0xf)
> @@ -371,3 +372,40 @@ void __hyp_text __vgic_v3_write_vmcr(u32 vmcr)
>  {
>  	write_gicreg(vmcr, ICH_VMCR_EL2);
>  }
> +
> +#ifdef CONFIG_ARM64
> +
> +int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
> +{
> +	int rt;
> +	u32 esr;
> +	u32 vmcr;
> +	void (*fn)(struct kvm_vcpu *, u32, int);
> +	bool is_read;
> +	u32 sysreg;
> +
> +	esr = kvm_vcpu_get_hsr(vcpu);
> +	if (vcpu_mode_is_32bit(vcpu)) {
> +		if (!kvm_condition_valid(vcpu))
> +			return 1;
> +
> +		sysreg = esr_cp15_to_sysreg(esr);
> +	} else {
> +		sysreg = esr_sys64_to_sysreg(esr);
> +	}
> +
> +	is_read = (esr & ESR_ELx_SYS64_ISS_DIR_MASK) == ESR_ELx_SYS64_ISS_DIR_READ;
> +
> +	switch (sysreg) {
> +	default:
> +		return 0;
> +	}
> +
> +	vmcr = __vgic_v3_read_vmcr();
> +	rt = kvm_vcpu_sys_get_rt(vcpu);
> +	fn(vcpu, vmcr, rt);
> +
> +	return 1;
> +}
> +
> +#endif
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index 6fe3f003636a..88d9bd9bf468 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -410,6 +410,8 @@ int vgic_v3_map_resources(struct kvm *kvm)
>  	return ret;
>  }
>  
> +DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
> +
>  /**
>   * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
>   * @node:	pointer to the DT node
> -- 
> 2.11.0
>