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Re: [PATCH v2] xen/public: add comment to struct xen_mem_acquire_resource
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 8 Feb 2022 13:39:35 +0100
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- Cc: George Dunlap <George.Dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 08 Feb 2022 12:39:52 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.02.2022 13:22, Juergen Gross wrote:
> On 08.02.22 12:55, Andrew Cooper wrote:
>> On 08/02/2022 07:42, Juergen Gross wrote:
>>> --- a/xen/include/public/memory.h
>>> +++ b/xen/include/public/memory.h
>>> @@ -662,6 +662,11 @@ struct xen_mem_acquire_resource {
>>> * two calls.
>>> */
>>> uint32_t nr_frames;
>>> + /*
>>> + * Padding field, must be zero on input.
>>> + * The lowest bit was named XENMEM_rsrc_acq_caller_owned in a previous
>>> + * version and should not be reused in future.
>>
>> s/should/will/. This is a statement of how Xen shall behave.
>
> Okay.
>
>> I think it's also worth somehow fitting in that it's an output only
>> bit. It will be important when inevitably we end up changing this back
>> to being a flags field when we need to extend the hypercall.
>
> Okay.
>
> In the end the bit only needs to be reserved, if pad _is_ zero on input.
> So the correct way to phrase it would be:
>
> /*
> * Padding field, must be zero on input.
> * In a previous version this was an output field with the lowest
> * bit named XENMEM_rsrc_acq_caller_owned. Future versions of this
> * interface will not reuse this bit with the field being zero on
> * input.
> */
>
> Is this fine with you?
FWIW it is at least fine with me this way.
Jan
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