linux-kernel - Re: [RFC v2 7/9] KVM: KVM-VFIO: add new VFIO external API hooks

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Date:	Thu, 11 Sep 2014 05:10:20 +0200
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	eric.auger@...com, marc.zyngier@....com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
	kvm@...r.kernel.org, alex.williamson@...hat.com,
	joel.schopp@....com, kim.phillips@...escale.com, paulus@...ba.org,
	gleb@...nel.org, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
	patches@...aro.org, will.deacon@....com,
	a.motakis@...tualopensystems.com, a.rigo@...tualopensystems.com,
	john.liuli@...wei.com
Subject: Re: [RFC v2 7/9] KVM: KVM-VFIO: add new VFIO external API hooks

On Mon, Sep 01, 2014 at 02:52:46PM +0200, Eric Auger wrote:
> add functions that implement the gateway to the extended

Capital letter when beginning a new sentence.  Also the reference to
'the extended VFIO API' feels a bit weird.  Can't you make your commit
message a little more descriptive of this patch, something along the
lines of:

Provide wrapper functions that allows KVM-VFIO device code to get an
external handle on a struct vfio_device based on a vfio device file
descriptor.  We provide this through three new functions:

(assuming I got this right).



> external VFIO API:
> - kvm_vfio_device_get_external_user
> - kvm_vfio_device_put_external_user
> - kvm_vfio_external_base_device
> 
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> 
> ---
> 
> v1 -> v2:
> - kvm_vfio_external_get_base_device renamed into
>   kvm_vfio_external_base_device
> - kvm_vfio_external_get_type removed
> ---
>  arch/arm/include/asm/kvm_host.h |  5 +++++
>  virt/kvm/vfio.c                 | 45 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 6dfb404..1aee6bb 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -171,6 +171,11 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
>  unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
>  int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
>  
> +struct vfio_device;
> +struct vfio_device *kvm_vfio_device_get_external_user(struct file *filep);
> +void kvm_vfio_device_put_external_user(struct vfio_device *vdev);
> +struct device *kvm_vfio_external_base_device(struct vfio_device *vdev);
> +
>  /* We do not have shadow page tables, hence the empty hooks */
>  static inline int kvm_age_hva(struct kvm *kvm, unsigned long hva)
>  {
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index ba1a93f..76dc7a1 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -59,6 +59,51 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
>  	symbol_put(vfio_group_put_external_user);
>  }
>  
> +struct vfio_device *kvm_vfio_device_get_external_user(struct file *filep)
> +{
> +	struct vfio_device *vdev;
> +	struct vfio_device *(*fn)(struct file *);
> +
> +	fn = symbol_get(vfio_device_get_external_user);
> +	if (!fn)
> +		return ERR_PTR(-EINVAL);
> +
> +	vdev = fn(filep);
> +
> +	symbol_put(vfio_device_get_external_user);
> +
> +	return vdev;
> +}
> +
> +void kvm_vfio_device_put_external_user(struct vfio_device *vdev)
> +{
> +	void (*fn)(struct vfio_device *);
> +
> +	fn = symbol_get(vfio_device_put_external_user);
> +	if (!fn)
> +		return;
> +
> +	fn(vdev);
> +
> +	symbol_put(vfio_device_put_external_user);
> +}
> +
> +struct device *kvm_vfio_external_base_device(struct vfio_device *vdev)
> +{
> +	struct device *(*fn)(struct vfio_device *);
> +	struct device *dev;
> +
> +	fn = symbol_get(vfio_external_base_device);
> +	if (!fn)
> +		return NULL;
> +
> +	dev = fn(vdev);
> +
> +	symbol_put(vfio_external_base_device);
> +
> +	return dev;
> +}
> +
>  static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
>  {
>  	long (*fn)(struct vfio_group *, unsigned long);
> -- 
> 1.9.1
> 

otherwise looks good to me!
-Christoffer
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