Re: [PATCH Kernel v18 6/7] vfio iommu: Add migration capability to report supported features

From: Alex Williamson <alex.williamson@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com,
	yi.l.liu@intel.com, cjia@nvidia.com, kvm@vger.kernel.org,
	eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org,
	cohuck@redhat.com, shuangtai.tst@alibaba-inc.com,
	dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com,
	pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com,
	felipe@nutanix.com, jonathan.davies@nutanix.com,
	yan.y.zhao@intel.com, changpeng.liu@intel.com, Ken.Xue@amd.com
Subject: Re: [PATCH Kernel v18 6/7] vfio iommu: Add migration capability to report supported features
Date: Wed, 6 May 2020 16:27:38 -0600	[thread overview]
Message-ID: <20200506162738.6e08dbf2@w520.home> (raw)
In-Reply-To: <1588607939-26441-7-git-send-email-kwankhede@nvidia.com>

On Mon, 4 May 2020 21:28:58 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> Added migration capability in IOMMU info chain.
> User application should check IOMMU info chain for migration capability
> to use dirty page tracking feature provided by kernel module.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 15 +++++++++++++++
>  include/uapi/linux/vfio.h       | 14 ++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 8b27faf1ec38..b38d278d7bff 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2378,6 +2378,17 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
>  	return ret;
>  }
>  
> +static int vfio_iommu_migration_build_caps(struct vfio_info_cap *caps)
> +{
> +	struct vfio_iommu_type1_info_cap_migration cap_mig;
> +
> +	cap_mig.header.id = VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION;
> +	cap_mig.header.version = 1;
> +	cap_mig.flags = VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK;
> +
> +	return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig));
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -2427,6 +2438,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  		if (ret)
>  			return ret;
>  
> +		ret = vfio_iommu_migration_build_caps(&caps);
> +		if (ret)
> +			return ret;
> +
>  		if (caps.size) {
>  			info.flags |= VFIO_IOMMU_INFO_CAPS;
>  
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index e3cbf8b78623..df9ce8aaafab 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -1013,6 +1013,20 @@ struct vfio_iommu_type1_info_cap_iova_range {
>  	struct	vfio_iova_range iova_ranges[];
>  };
>  
> +/*
> + * The migration capability allows to report supported features for migration.
> + *
> + * The structures below define version 1 of this capability.
> + */
> +#define VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION  1
> +
> +struct vfio_iommu_type1_info_cap_migration {
> +	struct	vfio_info_cap_header header;
> +	__u32	flags;
> +	/* supports dirty page tracking */
> +#define VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK	(1 << 0)
> +};
> +

What about exposing the maximum supported dirty bitmap size and the
supported page sizes?  Thanks,

Alex

>  #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>  
>  /**