Re: [Xen-devel] [PATCH v6 05/11] x86/hyperv: setup hypercall page

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.02.2020 12:21, Durrant, Paul wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 03 February 2020 11:06
>> To: Durrant, Paul <pdurrant@xxxxxxxxxxxx>
>> Cc: Wei Liu <wl@xxxxxxx>; Xen Development List <xen-
>> devel@xxxxxxxxxxxxxxxxxxxx>; Michael Kelley <mikelley@xxxxxxxxxxxxx>; Wei
>> Liu <liuwe@xxxxxxxxxxxxx>; Andrew Cooper <andrew.cooper3@xxxxxxxxxx>;
>> Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> Subject: Re: [PATCH v6 05/11] x86/hyperv: setup hypercall page
>>
>> On 03.02.2020 11:39, Durrant, Paul wrote:
>>>> -----Original Message-----
>>>> From: Wei Liu <wl@xxxxxxx>
>>>> Sent: 31 January 2020 17:57
>>>> To: Xen Development List <xen-devel@xxxxxxxxxxxxxxxxxxxx>
>>>> Cc: Durrant, Paul <pdurrant@xxxxxxxxxxxx>; Michael Kelley
>>>> <mikelley@xxxxxxxxxxxxx>; Wei Liu <liuwe@xxxxxxxxxxxxx>; Wei Liu
>>>> <wl@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Andrew Cooper
>>>> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>>> Subject: Re: [PATCH v6 05/11] x86/hyperv: setup hypercall page
>>>>
>>>> (Note to self)
>>>>
>>>> On Fri, Jan 31, 2020 at 05:49:24PM +0000, Wei Liu wrote:
>>>> [...]
>>>>> +static uint64_t generate_guest_id(void)
>>>>> +{
>>>>> +    union hv_guest_os_id id;
>>>>> +
>>>>
>>>>        id.raw = 0;
>>>
>>> Or just use a C99 initializer to set things up. A bit neater IMO.
>>
>> If you mean this for ...
>>
>>>>> +    id.vendor = HV_XEN_VENDOR_ID;
>>>>> +    id.major = xen_major_version();
>>>>> +    id.minor = xen_minor_version();
>>
>> ... these three fields, then this won't work with rather old gcc
>> we still permit to be used. Using { .raw = 0 } would work afaict.
>>
> 
> Not even { .vendor = HV_XEN_VENDOR_ID } ?

No, because of it being part of an unnamed (struct) member of
the union.

Jan

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