Re: [PATCH v3 04/15] argo: init, destroy and soft-reset, with enable command line opt

From: "Jan Beulich" <JBeulich@suse.com>
To: Jason Andryuk <jandryuk@gmail.com>
Cc: Tim Deegan <tim@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	ross.philipson@gmail.com,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Daniel Smith <dpsmith@apertussolutions.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	Christopher Clark <christopher.w.clark@gmail.com>,
	Rich Persaud <persaur@gmail.com>,
	James McKenzie <james@bromium.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Paul Durrant <paul.durrant@citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	eric chanudet <eric.chanudet@gmail.com>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH v3 04/15] argo: init, destroy and soft-reset, with enable command line opt
Date: Wed, 09 Jan 2019 02:35:07 -0700	[thread overview]
Message-ID: <5C35C04B020000780020BB8D@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <CAKf6xpvXBGUwFAjvwromG737Bg-_MB7rWBB=Oj7q2zHgaiF5mg@mail.gmail.com>

>>> On 08.01.19 at 23:54, <jandryuk@gmail.com> wrote:

First of all - please trim your replies.

> On Mon, Jan 7, 2019 at 2:43 AM Christopher Clark <christopher.w.clark@gmail.com> wrote:
>> --- a/docs/misc/xen-command-line.pandoc
>> +++ b/docs/misc/xen-command-line.pandoc
>> @@ -182,6 +182,17 @@ Permit Xen to use "Always Running APIC Timer" support on compatible hardware
>>  in combination with cpuidle.  This option is only expected to be useful for
>>  developers wishing Xen to fall back to older timing methods on newer hardware.
>>
>> +### argo
>> +> `= <boolean>`
>> +
>> +> Default: `false`
>> +
>> +Enable the Argo hypervisor-mediated interdomain communication mechanism.
>> +
>> +This allows domains access to the Argo hypercall, which supports registration
>> +of memory rings with the hypervisor to receive messages, sending messages to
>> +other domains by hypercall and querying the ring status of other domains.
>> +
> 
> Do we want to say it's only available when Xen is compiled with CONFIG_ARGO?

We don't do so elsewhere, so I'm with Christopher.

>> +     */
>> +    struct argo_ring_info *ring_info;
>> +    /* domain to be notified when space is available */
>> +    domid_t domain_id;
>> +    uint16_t pad;
> 
> Can we order domain_id after len and drop the pad?

That would still call for a pad field - we prefer to have explicit padding,
and also to check it's zero, the latter to allow for assigning meaning to
the field down the road.

Jan

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