From: "Jan Beulich" <JBeulich@suse.com>
To: Christopher Clark <christopher.w.clark@gmail.com>
Cc: Tim Deegan <tim@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
ross.philipson@gmail.com, Jason Andryuk <jandryuk@gmail.com>,
Daniel Smith <dpsmith@apertussolutions.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Ian Jackson <Ian.Jackson@eu.citrix.com>,
Rich Persaud <persaur@gmail.com>,
James McKenzie <voreekf@madingley.org>,
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 15/25] argo: implement the sendv op
Date: Fri, 04 Jan 2019 06:37:43 -0700 [thread overview]
Message-ID: <5C2F61A7020000780020A392@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <CACMJ4GbkBn692QsX9d-Y43YNN6N_foOCqJJQja0exDm7SNO8Aw@mail.gmail.com>
>>> On 04.01.19 at 09:13, <christopher.w.clark@gmail.com> wrote:
> ok, I'm at the point where I'm close to having a version three of the
> series to post that addresses all the feedback so far, plus some
> additional improvements, with the following two items remaining to
> discuss:
>
> 1) the domain_cookie, with Jan's question about a) its exclusion of
> mismatches and b) its utility.
>
> Given the expressed concern that the timer-based cookie initialization
> does not necessarily exclude mismatches, I've reimplemented it as a
> simple 128-bit counter protected by the L1 lock: this does now exclude
> mismatches.
... for all practical purposes, I assume you mean. In which case
I'd then immediately ask whether a 64-bit counter wouldn't do
as well.
> The utility of the cookie follows from this:
>
> domid, despite its name, is not a unique domain identifier; it's a
> temporally unique id: Xen will ensure that no two domains that execute
> concurrently have the same domid. Domain authentication needs to take
> this into account.
Correct, at which point the question arises whether domain IDs
aren't too narrow. After all this isn't the first time we run into such
a restriction - see the opt_ibpb related code in context_switch().
> With Argo, it affects these points:
>
> * ring registration: when the partner domain domid is specified, argo
> finds the currently executing domain with that domid, and needs to
> be able to confirm that it is the same domain later when a sendv is
> issued.
>
> * sendv: needs to confirm that the domain sending a message is the same
> as the single domain authorized to transmit when the ring was first
> registered.
>
> * notify: the querying domain asks about free space, and if there's not
> enough then a record is kept internal to the hypervisor, and a signal
> will be sent to the caller later when sufficient space becomes
> available. Before sending the signal, Xen needs to confirm that the
> current domain with the domid it remembered is the same as the one that
> issued the query, otherwise Xen is sending spurious signals to domains
> that are not expecting it (and unless it checks, may not even be
> argo-enabled).
>
> * domain teardown: in the absence of the domain cookie, or an
> alternative data structure that achieves the same ability to
> distinguish a reincarnated domain, all the rings that are registered
> that authorize the dying domid to send need to be torn down with
> suitable notification to their owners, and all the pending signals for
> that domain about available free space need to be nullified, to prevent
> a later domain inheriting these credentials and signals.
>
> Doing so either entails a potentially-expensive walk of all rings of all
> domains, plus all the pending notifications on all rings the domain can
> access, or additional complexity with new data structures storing
> further metadata on the authorized domain on ring registration, etc.
> The domain cookie which enables identity confirmation on a domid is
> a reasonable alternative solution.
For all of these the question then is whether holding a reference
to the other domain (which has been looked up during ring
registration) wouldn't help. Furthermore this isn't a new problem,
see e.g. how event channel code deals with the ECS_INTERDOMAIN
case - without acquiring extra references, but instead with suitable
(and mutual) cleanup during domain destruction.
Jan
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next prev parent reply other threads:[~2019-01-04 13:37 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-01 1:32 [PATCH 00/25] Argo: hypervisor-mediated interdomain communication Christopher Clark
2018-12-01 1:32 ` [PATCH 01/25] xen/evtchn: expose evtchn_bind_ipi_vcpu0_domain for use within Xen Christopher Clark
2018-12-03 16:20 ` Jan Beulich
2018-12-04 9:17 ` Christopher Clark
2018-12-01 1:32 ` [PATCH 02/25] argo: Introduce the Kconfig option to govern inclusion of Argo Christopher Clark
2018-12-03 15:51 ` Jan Beulich
2018-12-04 9:12 ` Christopher Clark
2018-12-01 1:32 ` [PATCH 03/25] argo: introduce the argo_message_op hypercall boilerplate Christopher Clark
2018-12-04 9:44 ` Paul Durrant
2018-12-20 5:13 ` Christopher Clark
2018-12-01 1:32 ` [PATCH 04/25] argo: define argo_dprintk for subsystem debugging Christopher Clark
2018-12-03 15:59 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 05/25] argo: Add initial argo_init and argo_destroy Christopher Clark
2018-12-04 9:12 ` Paul Durrant
2018-12-13 13:16 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 06/25] argo: Xen command line parameter 'argo': bool to enable/disable Christopher Clark
2018-12-04 9:18 ` Paul Durrant
2018-12-04 11:35 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 07/25] xen (ARM, x86): add errno-returning functions for copy Christopher Clark
2018-12-04 9:35 ` Paul Durrant
2018-12-12 16:01 ` Roger Pau Monné
2018-12-20 5:16 ` Christopher Clark
2018-12-20 8:45 ` Jan Beulich
2018-12-20 12:57 ` Roger Pau Monné
2018-12-01 1:32 ` [PATCH 08/25] xen: define XEN_GUEST_HANDLE_NULL as null XEN_GUEST_HANDLE Christopher Clark
2018-12-04 11:39 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 09/25] errno: add POSIX error codes EMSGSIZE, ECONNREFUSED to the ABI Christopher Clark
2018-12-03 15:42 ` Jan Beulich
2018-12-04 9:10 ` Christopher Clark
2018-12-04 10:04 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 10/25] arm: introduce guest_handle_for_field() Christopher Clark
2018-12-04 9:46 ` Paul Durrant
2018-12-01 1:32 ` [PATCH 11/25] xsm, argo: XSM control for argo register operation, argo_mac bootparam Christopher Clark
2018-12-04 9:52 ` Paul Durrant
2018-12-20 5:19 ` Christopher Clark
2018-12-01 1:32 ` [PATCH 12/25] xsm, argo: XSM control for argo message send operation Christopher Clark
2018-12-04 9:53 ` Paul Durrant
2018-12-01 1:32 ` [PATCH 13/25] argo: implement the register op Christopher Clark
2018-12-02 20:10 ` Julien Grall
2018-12-04 9:08 ` Christopher Clark
2018-12-05 17:20 ` Julien Grall
2018-12-05 22:35 ` Christopher Clark
2018-12-11 13:51 ` Julien Grall
2018-12-04 10:57 ` Paul Durrant
2018-12-12 9:48 ` Jan Beulich
2018-12-20 5:29 ` Christopher Clark
2018-12-20 8:29 ` Jan Beulich
2018-12-21 1:25 ` Christopher Clark
2018-12-21 7:28 ` Jan Beulich
2018-12-21 8:16 ` Christopher Clark
2018-12-21 8:53 ` Jan Beulich
2018-12-21 23:28 ` Christopher Clark
2018-12-12 16:47 ` Roger Pau Monné
2018-12-20 5:41 ` Christopher Clark
2018-12-20 8:51 ` Jan Beulich
2018-12-20 12:52 ` Roger Pau Monné
2018-12-21 23:05 ` Christopher Clark
2019-01-04 8:57 ` Roger Pau Monné
2019-01-04 13:22 ` Jan Beulich
2019-01-04 15:35 ` Roger Pau Monné
2019-01-04 15:47 ` Jan Beulich
2019-01-07 9:00 ` Roger Pau Monné
2019-01-09 16:15 ` Tamas K Lengyel
2019-01-09 16:23 ` Razvan Cojocaru
2019-01-09 16:34 ` Roger Pau Monné
2019-01-09 16:48 ` Razvan Cojocaru
2019-01-09 16:50 ` Tamas K Lengyel
2019-01-09 16:59 ` Roger Pau Monné
2019-01-09 17:03 ` Fwd: " Roger Pau Monné
2019-01-09 17:03 ` Razvan Cojocaru
2018-12-01 1:32 ` [PATCH 14/25] argo: implement the unregister op Christopher Clark
2018-12-04 11:10 ` Paul Durrant
2018-12-12 9:51 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 15/25] argo: implement the sendv op Christopher Clark
2018-12-04 11:22 ` Paul Durrant
2018-12-12 11:52 ` Jan Beulich
2018-12-20 5:58 ` Christopher Clark
2018-12-20 8:33 ` Jan Beulich
2019-01-04 8:13 ` Christopher Clark
2019-01-04 8:43 ` Roger Pau Monné
2019-01-04 13:37 ` Jan Beulich [this message]
2019-01-07 20:54 ` Christopher Clark
2018-12-01 1:32 ` [PATCH 16/25] argo: implement the notify op Christopher Clark
2018-12-13 14:06 ` Jan Beulich
2018-12-20 6:12 ` Christopher Clark
2018-12-20 8:39 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 17/25] xsm, argo: XSM control for any access to argo by a domain Christopher Clark
2018-12-01 1:32 ` [PATCH 18/25] argo: limit the max number of rings that a domain may register Christopher Clark
2018-12-13 14:08 ` Jan Beulich
2018-12-01 1:32 ` [PATCH 19/25] argo: limit the max number of notify requests in a single operation Christopher Clark
2018-12-01 1:32 ` [PATCH 20/25] argo, xsm: notify: don't describe rings that cannot be sent to Christopher Clark
2018-12-01 1:33 ` [PATCH 21/25] argo: add array_index_nospec to guard the result of the hash func Christopher Clark
2018-12-13 14:10 ` Jan Beulich
2018-12-01 1:33 ` [PATCH 22/25] xen/evtchn: expose send_guest_global_virq for use within Xen Christopher Clark
2018-12-13 14:12 ` Jan Beulich
2018-12-01 1:33 ` [PATCH 23/25] argo: signal x86 HVM and ARM via VIRQ Christopher Clark
2018-12-02 19:55 ` Julien Grall
2018-12-04 9:03 ` Christopher Clark
2018-12-04 9:16 ` Paul Durrant
2018-12-12 14:49 ` James
2018-12-11 14:15 ` Julien Grall
2018-12-13 14:16 ` Jan Beulich
2018-12-20 6:20 ` Christopher Clark
2018-12-01 1:33 ` [PATCH 24/25] argo: unmap rings on suspend and send signal to ring-owners on resume Christopher Clark
2018-12-13 14:26 ` Jan Beulich
2018-12-20 6:25 ` Christopher Clark
2018-12-01 1:33 ` [PATCH 25/25] argo: implement the get_config op to query notification config Christopher Clark
2018-12-13 14:32 ` Jan Beulich
2018-12-03 16:49 ` [PATCH 00/25] Argo: hypervisor-mediated interdomain communication Chris Patterson
2018-12-04 9:00 ` Christopher Clark
2018-12-11 22:13 ` Chris Patterson
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