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

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Message-ID: <eb50b355-06f9-c93f-3600-56af4a53f4c0@linux.microsoft.com>
Date: Fri, 23 Jan 2026 16:36:28 -0800
From: Mukesh R <mrathor@...ux.microsoft.com>
To: Nuno Das Neves <nunodasneves@...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 1/23/26 10:25, Nuno Das Neves wrote:
> 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.
> 


Correct, I switched it because the next patch won't compile without it as
it needs the declarations here. It could be combined into one big patch,
but I think normally one would not expect full functionality until the
release is certified to be that feature compliant anyways. Hope that
makes sense.

Thanks,
-Mukesh




>>   /*
>>    ********************************
>> @@ -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