From: Paul Durrant <xadimgnik@gmail.com>
To: "'Jürgen Groß'" <jgross@suse.com>,
"'Julien Grall'" <julien@xen.org>,
xen-devel@lists.xenproject.org
Cc: 'Stefano Stabellini' <sstabellini@kernel.org>,
'Wei Liu' <wl@xen.org>,
'Andrew Cooper' <andrew.cooper3@citrix.com>,
'Paul Durrant' <pdurrant@amazon.com>,
'Ian Jackson' <ian.jackson@eu.citrix.com>,
'George Dunlap' <george.dunlap@citrix.com>,
'Jan Beulich' <jbeulich@suse.com>
Subject: RE: [PATCH v4] docs/designs: re-work the xenstore migration document...
Date: Tue, 28 Apr 2020 15:50:16 +0100 [thread overview]
Message-ID: <000f01d61d6c$5583e8f0$008bbad0$@xen.org> (raw)
In-Reply-To: <bb0a87e5-4112-107a-b15b-0edf1e616f87@suse.com>
> -----Original Message-----
> From: Jürgen Groß <jgross@suse.com>
> Sent: 28 April 2020 13:56
> To: paul@xen.org; 'Julien Grall' <julien@xen.org>; xen-devel@lists.xenproject.org
> Cc: 'Paul Durrant' <pdurrant@amazon.com>; 'Andrew Cooper' <andrew.cooper3@citrix.com>; 'George Dunlap'
> <george.dunlap@citrix.com>; 'Ian Jackson' <ian.jackson@eu.citrix.com>; 'Jan Beulich'
> <jbeulich@suse.com>; 'Stefano Stabellini' <sstabellini@kernel.org>; 'Wei Liu' <wl@xen.org>
> Subject: Re: [PATCH v4] docs/designs: re-work the xenstore migration document...
>
> On 28.04.20 14:46, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Julien Grall <julien@xen.org>
> >> Sent: 28 April 2020 11:23
> >> To: Jürgen Groß <jgross@suse.com>; Paul Durrant <paul@xen.org>; xen-devel@lists.xenproject.org
> >> Cc: Paul Durrant <pdurrant@amazon.com>; Andrew Cooper <andrew.cooper3@citrix.com>; George Dunlap
> >> <george.dunlap@citrix.com>; Ian Jackson <ian.jackson@eu.citrix.com>; Jan Beulich
> <jbeulich@suse.com>;
> >> Stefano Stabellini <sstabellini@kernel.org>; Wei Liu <wl@xen.org>
> >> Subject: Re: [PATCH v4] docs/designs: re-work the xenstore migration document...
> >>
> >> Hi Juergen,
> >>
> >> On 28/04/2020 11:10, Jürgen Groß wrote:
> >>> On 28.04.20 11:05, Julien Grall wrote:
> >>>>> -where tx_id is the non-zero identifier values of an open transaction.
> >>>>> +| Field | Description |
> >>>>> +|-----------|---------------------------------------------------|
> >>>>> +| `domid` | The domain-id that owns the shared page |
> >>>>> +| | |
> >>>>> +| `tdomid` | The domain-id that `domid` acts on behalf of if |
> >>>>> +| | it has been subject to an SET_TARGET |
> >>>>> +| | operation [2] or DOMID_INVALID [3] otherwise |
> >>>>> +| | |
> >>>>> +| `flags` | Must be zero |
> >>>>> +| | |
> >>>>> +| `evtchn` | The port number of the interdomain channel used |
> >>>>> +| | by `domid` to communicate with xenstored |
> >>>>> +| | |
> >>>>> +| `mfn` | The MFN of the shared page for a live update or |
> >>>>> +| | ~0 (i.e. all bits set) otherwise |
> >>>>> -### Protocol Extension
> >>>>> +Since the ABI guarantees that entry 1 in `domid`'s grant table will
> >>>>> always
> >>>>> +contain the GFN of the shared page, so for a live update `mfn` can
> >>>>> be used to
> >>>>> +give confidence that `domid` has not been re-cycled during the update.
> >>>>
> >>>> I am confused, there is no way a XenStored running in an Arm domain
> >>>> can map the MFN of the shared page. So how is this going to work out?
> >>>
> >>> I guess this will be a MFN for PV guests and a guest PFN else.
> >>
> >> If we use Xen terminology (xen/include/xen/mm.h), this would be a GFN.
> >>
> >
> > TBH I'm not sure a GFN would give much confidence about domain recycling as it would likely be the
> same for many domains, I think. We really need a UUID.
>
> No, we need a per-host domain value, which is associated with a domain
> and which is unique during the life-time of the host.
>
> E.g. a global counter, which is incremented at each domain creation and
> stored in struct domain.
>
Can we just drop this and fall back on the fact that libxl now prevents domids from being recycled for 60s?
Paul
next prev parent reply other threads:[~2020-04-28 14:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 15:50 [PATCH v4] docs/designs: re-work the xenstore migration document Paul Durrant
2020-04-27 15:55 ` Jürgen Groß
2020-04-28 9:05 ` Julien Grall
2020-04-28 10:10 ` Jürgen Groß
2020-04-28 10:23 ` Julien Grall
2020-04-28 12:46 ` Paul Durrant
2020-04-28 12:56 ` Jürgen Groß
2020-04-28 14:50 ` Paul Durrant [this message]
2020-04-28 14:51 ` Jürgen Groß
2020-04-28 12:47 ` Paul Durrant
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