On 28.08.2020 13:08, Paul Durrant wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeul...@suse.com>
>> Sent: 26 August 2020 15:03
>> To: Paul Durrant <p...@xen.org>
>> Cc: xen-devel@lists.xenproject.org; Durrant, Paul <pdurr...@amazon.co.uk>;
>> Ian Jackson
>> <ian.jack...@eu.citrix.com>; Wei Liu <w...@xen.org>; Andrew Cooper
>> <andrew.coop...@citrix.com>; George
>> Dunlap <george.dun...@citrix.com>; Julien Grall <jul...@xen.org>; Stefano
>> Stabellini
>> <sstabell...@kernel.org>; Roger Pau Monné <roger....@citrix.com>
>> Subject: RE: [EXTERNAL] [PATCH v7 8/9] x86/time: add a domain context record
>> for tsc_info...
>>
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>>
>> On 18.08.2020 12:30, Paul Durrant wrote:
>>> --- a/xen/include/public/save.h
>>> +++ b/xen/include/public/save.h
>>> @@ -93,7 +93,18 @@ struct domain_shared_info_context {
>>>
>>> DECLARE_DOMAIN_SAVE_TYPE(SHARED_INFO, 2, struct
>>> domain_shared_info_context);
>>>
>>> -#define DOMAIN_SAVE_CODE_MAX 2
>>> +#if defined(__i386__) || defined(__x86_64__)
>>> +struct domain_tsc_info_context {
>>> + uint32_t mode;
>>> + uint32_t incarnation;
>>> + uint64_t elapsed_nsec;
>>> + uint32_t khz;
>>> +};
>>
>> sizeof() for this struct varies between 32-bit and 64-bit - is
>> this not a problem? (alignof() varies too, but there I think
>> it's indeed not a problem, albeit it could still be taken care
>> of by using uint64_aligned_t, alongside the addition of an
>> explicit padding field).
>
> I don't think it should matter because domain context records have
> implicit padding to align up to the next 64-bit boundary,
Could you remind me where this is written down and enforced?
> so as long as fields within the struct don't move (which I think
> is true in this case) then we should be ok.
Right.
Jan
