linux-kernel - Re: [PATCH 3/7] KVM: arm: guest debug, add stub KVM_SET_GUEST

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Message-ID: <20141129162100.GE23653@cbox>
Date:	Sat, 29 Nov 2014 17:21:00 +0100
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Alex Bennée <alex.bennee@...aro.org>
Cc:	kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
	peter.maydell@...aro.org, agraf@...e.de, jan.kiszka@...mens.com,
	dahi@...ux.vnet.ibm.com, r65777@...escale.com, bp@...e.de,
	pbonzini@...hat.com, Gleb Natapov <gleb@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	Russell King <linux@....linux.org.uk>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] KVM: arm: guest debug, add stub KVM_SET_GUEST_DEBUG
 ioctl

On Tue, Nov 25, 2014 at 04:10:01PM +0000, Alex Bennée wrote:
> This commit adds a stub function to support the KVM_SET_GUEST_DEBUG
> ioctl. Currently any operation flag will return EINVAL. Actual
> functionality will be added with further patches.
> 
> Signed-off-by: Alex Bennée <alex.bennee@...aro.org>.
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 7610eaa..2c6386e 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2570,7 +2570,7 @@ handled.
>  4.87 KVM_SET_GUEST_DEBUG
>  
>  Capability: KVM_CAP_SET_GUEST_DEBUG
> -Architectures: x86, s390, ppc
> +Architectures: x86, s390, ppc, arm64
>  Type: vcpu ioctl
>  Parameters: struct kvm_guest_debug (in)
>  Returns: 0 on success; -1 on error
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 9e193c8..a0ff410 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -180,6 +180,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_ARM_PSCI:
>  	case KVM_CAP_ARM_PSCI_0_2:
>  	case KVM_CAP_READONLY_MEM:
> +	case KVM_CAP_SET_GUEST_DEBUG:

Don't we usually wait with introducing visibility to user space until
you actually do support the ioctl?

>  		r = 1;
>  		break;
>  	case KVM_CAP_COALESCED_MMIO:
> @@ -302,7 +303,34 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  					struct kvm_guest_debug *dbg)
>  {
> -	return -EINVAL;
> +	/* If it's not enabled clear all flags */
> +	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
> +		vcpu->guest_debug = 0;
> +		return 0;
> +	}
> +
> +	vcpu->guest_debug = dbg->control;
> +	kvm_info("%s: guest_debug is 0x%lx\n", __func__, vcpu->guest_debug);
> +
> +	/* Single Step */
> +	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> +		kvm_info("SS requested, not yet implemented\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Software Break Points */
> +	if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> +		kvm_info("SW BP support requested, not yet implemented\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Hardware assisted Break and Watch points */
> +	if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) {
> +		kvm_info("HW BP support requested, not yet implemented\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
>  }
>  
>  
> -- 
> 2.1.3
> 
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