Subject: Re: [PATCH v0 09/15] mshv: Import data structs around device domains and irq remapping

From: Mukesh R <[email-masked]>
Date: Fri, 23 Jan 2026 16:38:56 -0800

On 1/20/26 14:17, Stanislav Kinsburskii wrote:
> On Mon, Jan 19, 2026 at 10:42:24PM -0800, Mukesh R wrote:
>> From: Mukesh Rathor <[email-masked]>
>>
>> Import/copy from Hyper-V public headers, definitions and declarations that
>> are related to attaching and detaching of device domains and interrupt
>> remapping, and building device ids for those purposes.
>>
>> Signed-off-by: Mukesh Rathor <[email-masked]>
>> ---
>>   include/hyperv/hvgdk_mini.h |  11 ++++
>>   include/hyperv/hvhdk_mini.h | 112 ++++++++++++++++++++++++++++++++++++
>>   2 files changed, 123 insertions(+)
>>
> 
> <snip>
> 
>> +/* ID for stage 2 default domain and NULL domain */
>> +#define HV_DEVICE_DOMAIN_ID_S2_DEFAULT 0
>> +#define HV_DEVICE_DOMAIN_ID_S2_NULL    0xFFFFFFFFULL
>> +
>> +union hv_device_domain_id {
>> +	u64 as_uint64;
>> +	struct {
>> +		u32 type : 4;
>> +		u32 reserved : 28;
>> +		u32 id;
>> +	};
>> +} __packed;
> 
> Shouldn't the inner struct be packed instead?
> 
>> +
>> +struct hv_input_device_domain { /* HV_INPUT_DEVICE_DOMAIN */
>> +	u64 partition_id;
>> +	union hv_input_vtl owner_vtl;
>> +	u8 padding[7];
>> +	union hv_device_domain_id domain_id;
>> +} __packed;
>> +
>> +union hv_create_device_domain_flags {	/* HV_CREATE_DEVICE_DOMAIN_FLAGS */
>> +	u32 as_uint32;
>> +	struct {
>> +		u32 forward_progress_required : 1;
>> +		u32 inherit_owning_vtl : 1;
>> +		u32 reserved : 30;
>> +	} __packed;
>> +} __packed;
> 
> Why should the union be packed?

 From GCC docs:

Specifying this attribute for struct and union types is equivalent to
specifying the packed attribute on each of the structure or union members.

Thanks,
-Mukesh

> Thanks,
> Stanislav
> 
>> +
>> +struct hv_input_create_device_domain {	/* HV_INPUT_CREATE_DEVICE_DOMAIN */
>> +	struct hv_input_device_domain device_domain;
>> +	union hv_create_device_domain_flags create_device_domain_flags;
>> +} __packed;
>> +
>> +struct hv_input_delete_device_domain {	/* HV_INPUT_DELETE_DEVICE_DOMAIN */
>> +	struct hv_input_device_domain device_domain;
>> +} __packed;
>> +
>> +struct hv_input_attach_device_domain {	/* HV_INPUT_ATTACH_DEVICE_DOMAIN */
>> +	struct hv_input_device_domain device_domain;
>> +	union hv_device_id device_id;
>> +} __packed;
>> +
>> +struct hv_input_detach_device_domain {	/* HV_INPUT_DETACH_DEVICE_DOMAIN */
>> +	u64 partition_id;
>> +	union hv_device_id device_id;
>> +} __packed;
>> +
>> +struct hv_input_map_device_gpa_pages {	/* HV_INPUT_MAP_DEVICE_GPA_PAGES */
>> +	struct hv_input_device_domain device_domain;
>> +	union hv_input_vtl target_vtl;
>> +	u8 padding[3];
>> +	u32 map_flags;
>> +	u64 target_device_va_base;
>> +	u64 gpa_page_list[];
>> +} __packed;
>> +
>> +struct hv_input_unmap_device_gpa_pages {  /* HV_INPUT_UNMAP_DEVICE_GPA_PAGES */
>> +	struct hv_input_device_domain device_domain;
>> +	u64 target_device_va_base;
>> +} __packed;
>> +
>>   #endif /* _HV_HVHDK_MINI_H */
>> -- 
>> 2.51.2.vfs.0.1
>>