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

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Message-ID: <541162AB.5070303@linaro.org>
Date:	Thu, 11 Sep 2014 10:51:55 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Christoffer Dall <christoffer.dall@...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 09/11/2014 05:10 AM, Christoffer Dall wrote:
> 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).
sure
> 
> 
> 
>> 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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