Re: [PATCH 06/10] viridian: add ExProcessorMasks variants of the flush hypercalls

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.11.2020 17:11, Paul Durrant wrote:
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 12 November 2020 09:19
>>
>> On 11.11.2020 21:07, Paul Durrant wrote:
>>> --- a/xen/arch/x86/hvm/viridian/viridian.c
>>> +++ b/xen/arch/x86/hvm/viridian/viridian.c
>>> @@ -553,6 +553,83 @@ static unsigned int vpmask_next(struct 
>>> hypercall_vpmask *vpmask, unsigned int
>> vp
>>>          (vp) < HVM_MAX_VCPUS; \
>>>          (vp) = vpmask_next(vpmask, vp))
>>>
>>> +struct hypercall_vpset {
>>> +        struct hv_vpset set;
>>> +        uint64_t __bank_contents[64];
>>
>> gcc documents this to be supported as an extension; did you check
>> clang supports this, too?
> 
> By 'this', do you mean the assumption that that memory layout is consecutive?

No, rather the basic language aspect that in standard C a struct
member which is a struct ending in a flexible array member may
not be followed by any other field.

Jan