linux-kernel - Re: [PATCH v6 09/22] vfio: VFIO_IOMMU_BIND/UNBIND

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Date:   Thu, 21 Mar 2019 17:01:59 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, joro@...tes.org,
        jacob.jun.pan@...ux.intel.com, yi.l.liu@...ux.intel.com,
        jean-philippe.brucker@....com, will.deacon@....com,
        robin.murphy@....com, kevin.tian@...el.com, ashok.raj@...el.com,
        marc.zyngier@....com, christoffer.dall@....com,
        peter.maydell@...aro.org, vincent.stehle@....com
Subject: Re: [PATCH v6 09/22] vfio: VFIO_IOMMU_BIND/UNBIND_MSI

On Sun, 17 Mar 2019 18:22:19 +0100
Eric Auger <eric.auger@...hat.com> wrote:

> This patch adds the VFIO_IOMMU_BIND/UNBIND_MSI ioctl which aim
> to pass/withdraw the guest MSI binding to/from the host.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> 
> ---
> v3 -> v4:
> - add UNBIND
> - unwind on BIND error
> 
> v2 -> v3:
> - adapt to new proto of bind_guest_msi
> - directly use vfio_iommu_for_each_dev
> 
> v1 -> v2:
> - s/vfio_iommu_type1_guest_msi_binding/vfio_iommu_type1_bind_guest_msi
> ---
>  drivers/vfio/vfio_iommu_type1.c | 58 +++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 29 +++++++++++++++++
>  2 files changed, 87 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 12a40b9db6aa..66513679081b 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1710,6 +1710,25 @@ static int vfio_cache_inv_fn(struct device *dev, void *data)
>  	return iommu_cache_invalidate(d, dev, &ustruct->info);
>  }
>  
> +static int vfio_bind_msi_fn(struct device *dev, void *data)
> +{
> +	struct vfio_iommu_type1_bind_msi *ustruct =
> +		(struct vfio_iommu_type1_bind_msi *)data;
> +	struct iommu_domain *d = iommu_get_domain_for_dev(dev);
> +
> +	return iommu_bind_guest_msi(d, dev, ustruct->iova,
> +				    ustruct->gpa, ustruct->size);
> +}
> +
> +static int vfio_unbind_msi_fn(struct device *dev, void *data)
> +{
> +	dma_addr_t *iova = (dma_addr_t *)data;
> +	struct iommu_domain *d = iommu_get_domain_for_dev(dev);

Same as previous, we can encapsulate domain in our own struct to avoid
a lookup.

> +
> +	iommu_unbind_guest_msi(d, dev, *iova);

Is it strange that iommu-core is exposing these interfaces at a device
level if every one of them requires us to walk all the devices?  Thanks,

Alex

> +	return 0;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -1814,6 +1833,45 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  					      vfio_cache_inv_fn);
>  		mutex_unlock(&iommu->lock);
>  		return ret;
> +	} else if (cmd == VFIO_IOMMU_BIND_MSI) {
> +		struct vfio_iommu_type1_bind_msi ustruct;
> +		int ret;
> +
> +		minsz = offsetofend(struct vfio_iommu_type1_bind_msi,
> +				    size);
> +
> +		if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (ustruct.argsz < minsz || ustruct.flags)
> +			return -EINVAL;
> +
> +		mutex_lock(&iommu->lock);
> +		ret = vfio_iommu_for_each_dev(iommu, &ustruct,
> +					      vfio_bind_msi_fn);
> +		if (ret)
> +			vfio_iommu_for_each_dev(iommu, &ustruct.iova,
> +						vfio_unbind_msi_fn);
> +		mutex_unlock(&iommu->lock);
> +		return ret;
> +	} else if (cmd == VFIO_IOMMU_UNBIND_MSI) {
> +		struct vfio_iommu_type1_unbind_msi ustruct;
> +		int ret;
> +
> +		minsz = offsetofend(struct vfio_iommu_type1_unbind_msi,
> +				    iova);
> +
> +		if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (ustruct.argsz < minsz || ustruct.flags)
> +			return -EINVAL;
> +
> +		mutex_lock(&iommu->lock);
> +		ret = vfio_iommu_for_each_dev(iommu, &ustruct.iova,
> +					      vfio_unbind_msi_fn);
> +		mutex_unlock(&iommu->lock);
> +		return ret;
>  	}
>  
>  	return -ENOTTY;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 29f0ef2d805d..6763389b6adc 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -789,6 +789,35 @@ struct vfio_iommu_type1_cache_invalidate {
>  };
>  #define VFIO_IOMMU_CACHE_INVALIDATE      _IO(VFIO_TYPE, VFIO_BASE + 24)
>  
> +/**
> + * VFIO_IOMMU_BIND_MSI - _IOWR(VFIO_TYPE, VFIO_BASE + 25,
> + *			struct vfio_iommu_type1_bind_msi)
> + *
> + * Pass a stage 1 MSI doorbell mapping to the host so that this
> + * latter can build a nested stage2 mapping
> + */
> +struct vfio_iommu_type1_bind_msi {
> +	__u32   argsz;
> +	__u32   flags;
> +	__u64	iova;
> +	__u64	gpa;
> +	__u64	size;
> +};
> +#define VFIO_IOMMU_BIND_MSI      _IO(VFIO_TYPE, VFIO_BASE + 25)
> +
> +/**
> + * VFIO_IOMMU_UNBIND_MSI - _IOWR(VFIO_TYPE, VFIO_BASE + 26,
> + *			struct vfio_iommu_type1_unbind_msi)
> + *
> + * Unregister an MSI mapping
> + */
> +struct vfio_iommu_type1_unbind_msi {
> +	__u32   argsz;
> +	__u32   flags;
> +	__u64	iova;
> +};
> +#define VFIO_IOMMU_UNBIND_MSI      _IO(VFIO_TYPE, VFIO_BASE + 26)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*