linux-kernel - Re: [PATCH v0 05/15] mshv: Declarations and definitions for VFIO-MSHV bridge device

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Message-ID: <eeb79431-47e6-4334-b97a-4dd64474e539@linux.microsoft.com>
Date: Fri, 23 Jan 2026 10:25:36 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Mukesh R <mrathor@...ux.microsoft.com>, linux-kernel@...r.kernel.org,
 linux-hyperv@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 iommu@...ts.linux.dev, linux-pci@...r.kernel.org, linux-arch@...r.kernel.org
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
 decui@...rosoft.com, longli@...rosoft.com, catalin.marinas@....com,
 will@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, joro@...tes.org,
 lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
 robh@...nel.org, bhelgaas@...gle.com, arnd@...db.de, mhklinux@...look.com,
 romank@...ux.microsoft.com
Subject: Re: [PATCH v0 05/15] mshv: Declarations and definitions for VFIO-MSHV
 bridge device

On 1/19/2026 10:42 PM, Mukesh R wrote:
> From: Mukesh Rathor <mrathor@...ux.microsoft.com>
> 
> Add data structs needed by the subsequent patch that introduces a new
> module to implement VFIO-MSHV pseudo device.
> 
> Signed-off-by: Mukesh Rathor <mrathor@...ux.microsoft.com>
> ---
>  drivers/hv/mshv_root.h    | 23 +++++++++++++++++++++++
>  include/uapi/linux/mshv.h | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 54 insertions(+)
> 
> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
> index c3753b009fd8..42e1da1d545b 100644
> --- a/drivers/hv/mshv_root.h
> +++ b/drivers/hv/mshv_root.h
> @@ -220,6 +220,29 @@ struct port_table_info {
>  	};
>  };
>  
> +struct mshv_device {
> +	const struct mshv_device_ops *device_ops;
> +	struct mshv_partition *device_pt;
> +	void *device_private;
> +	struct hlist_node device_ptnode;
> +};
> +
> +struct mshv_device_ops {
> +	const char *device_name;
> +	long (*device_create)(struct mshv_device *dev, u32 type);
> +	void (*device_release)(struct mshv_device *dev);
> +	long (*device_set_attr)(struct mshv_device *dev,
> +				struct mshv_device_attr *attr);
> +	long (*device_has_attr)(struct mshv_device *dev,
> +				struct mshv_device_attr *attr);
> +};
> +
> +extern struct mshv_device_ops mshv_vfio_device_ops;
> +int mshv_vfio_ops_init(void);
> +void mshv_vfio_ops_exit(void);
> +long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
> +					void __user *user_args);
> +
>  int mshv_update_routing_table(struct mshv_partition *partition,
>  			      const struct mshv_user_irq_entry *entries,
>  			      unsigned int numents);
> diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
> index dee3ece28ce5..b7b10f9e2896 100644
> --- a/include/uapi/linux/mshv.h
> +++ b/include/uapi/linux/mshv.h
> @@ -252,6 +252,7 @@ struct mshv_root_hvcall {
>  #define MSHV_GET_GPAP_ACCESS_BITMAP	_IOWR(MSHV_IOCTL, 0x06, struct mshv_gpap_access_bitmap)
>  /* Generic hypercall */
>  #define MSHV_ROOT_HVCALL		_IOWR(MSHV_IOCTL, 0x07, struct mshv_root_hvcall)
> +#define MSHV_CREATE_DEVICE		_IOWR(MSHV_IOCTL, 0x08, struct mshv_create_device)
>  

With this commit, the IOCTL number is exposed to userspace but it doesn't work.
Ideally the IOCTL number should be added in the commit where it becomes usable.

>  /*
>   ********************************
> @@ -402,4 +403,34 @@ struct mshv_sint_mask {
>  /* hv_hvcall device */
>  #define MSHV_HVCALL_SETUP        _IOW(MSHV_IOCTL, 0x1E, struct mshv_vtl_hvcall_setup)
>  #define MSHV_HVCALL              _IOWR(MSHV_IOCTL, 0x1F, struct mshv_vtl_hvcall)
> +
> +/* device passhthru */
> +#define MSHV_CREATE_DEVICE_TEST		1
> +
> +enum {
> +	MSHV_DEV_TYPE_VFIO,
> +	MSHV_DEV_TYPE_MAX,
> +};
> +
> +struct mshv_create_device {
> +	__u32	type;	     /* in: MSHV_DEV_TYPE_xxx */
> +	__u32	fd;	     /* out: device handle */
> +	__u32	flags;	     /* in: MSHV_CREATE_DEVICE_xxx */
> +};
> +
> +#define MSHV_DEV_VFIO_FILE      1
> +#define MSHV_DEV_VFIO_FILE_ADD	1
> +#define MSHV_DEV_VFIO_FILE_DEL	2
> +
> +struct mshv_device_attr {
> +	__u32	flags;		/* no flags currently defined */
> +	__u32	group;		/* device-defined */
> +	__u64	attr;		/* group-defined */
> +	__u64	addr;		/* userspace address of attr data */
> +};
> +
> +/* Device fds created with MSHV_CREATE_DEVICE */
> +#define MSHV_SET_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x00, struct mshv_device_attr)
> +#define MSHV_HAS_DEVICE_ATTR	_IOW(MSHV_IOCTL, 0x01, struct mshv_device_attr)
> +
>  #endif