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 13/25] argo: implement the register op
Date: Thu, 20 Dec 2018 01:29:19 -0700 [thread overview]
Message-ID: <5C1B52DF0200007800207E5A@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <CACMJ4Gama2ewm71wvWZFV4+LmrSDr_prajw2XAGZ5Kt3XsP7kQ@mail.gmail.com>
>>> On 20.12.18 at 06:29, <christopher.w.clark@gmail.com> wrote:
> On Wed, Dec 12, 2018 at 1:48 AM Jan Beulich <JBeulich@suse.com> wrote:
>>
>> > +static int
>> > +argo_find_ring_mfns(struct domain *d, struct argo_ring_info *ring_info,
>> > + uint32_t npage, XEN_GUEST_HANDLE_PARAM(argo_pfn_t) pfn_hnd,
>> > + uint32_t len)
>> > +{
>> > + int i;
>> > + int ret = 0;
>> > +
>> > + if ( (npage << PAGE_SHIFT) < len )
>> > + return -EINVAL;
>> > +
>> > + if ( ring_info->mfns )
>> > + {
>> > + /*
>> > + * Ring already existed. Check if it's the same ring,
>> > + * i.e. same number of pages and all translated gpfns still
>> > + * translating to the same mfns
>> > + */
>>
>> This comment makes me wonder whether the translations are
>> permitted to change at other times. If so I'm not sure what
>> value verification here has. If not, this probably would want to
>> be debugging-only code.
>
> My understanding is that the gfn->mfn translation is not necessarily stable
> across entry and exit from host power state S4, suspend to disk.
How would that be? It's not stable across guest migration (or
its non-live save/restore equivalent), but how would things
change across S3? And there's no support for S4 (and I can't
see it appearing any time soon).
>> > +static struct argo_ring_info *
>> > +argo_ring_find_info(const struct domain *d, const struct argo_ring_id *id)
>> > +{
>> > + uint16_t hash;
>> > + struct hlist_node *node;
>>
>> const?
>
> I couldn't determine exactly what you were pointing towards with this one.
> I've applied 'const' in a lot further place in the next version; please
> let me know if I've missed where you intended.
This is a pretty general rule: const should be applied to pointer
target types whenever no modification is intended, to make
this read-only aspect very obvious (and force people to think
twice if they alter such a property).
>> > + uint64_t dst_domain_cookie = 0;
>> > +
>> > + if ( !(guest_handle_is_aligned(ring_hnd, ~PAGE_MASK)) )
>> > + return -EINVAL;
>>
>> Why? You don't store the handle for later use (and you shouldn't).
>> If there really is a need for a full page's worth of memory, it
>> would better be passed in as GFN.
>
> I've added this comment for this behaviour in v2:
>
> + /*
> + * Verify the alignment of the ring data structure supplied with the
> + * understanding that the ring handle supplied points to the same memory as
> + * the first entry in the array of pages provided via pg_descr_hnd, where
> + * the head of the ring will reside.
> + * See argo_update_tx_ptr where the location of the tx_ptr is accessed at a
> + * fixed offset from head of the first page in the mfn array.
> + */
Well, this then suggests that you don't want to verify alignment,
but instead you want to verify addresses match.
>> > @@ -253,6 +723,34 @@ do_argo_message_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg1,
>> >
>> > switch (cmd)
>> > {
>> > + case ARGO_MESSAGE_OP_register_ring:
>> > + {
>> > + XEN_GUEST_HANDLE_PARAM(argo_ring_t) ring_hnd =
>> > + guest_handle_cast(arg1, argo_ring_t);
>> > + XEN_GUEST_HANDLE_PARAM(argo_pfn_t) pfn_hnd =
>> > + guest_handle_cast(arg2, argo_pfn_t);
>> > + uint32_t npage = arg3;
>> > + bool fail_exist = arg4 & ARGO_REGISTER_FLAG_FAIL_EXIST;
>> > +
>> > + if ( unlikely(!guest_handle_okay(ring_hnd, 1)) )
>> > + break;
>>
>> I don't understand the need for this and ...
>>
>> > + if ( unlikely(npage > (ARGO_MAX_RING_SIZE >> PAGE_SHIFT)) )
>> > + {
>> > + rc = -EINVAL;
>> > + break;
>> > + }
>> > + if ( unlikely(!guest_handle_okay(pfn_hnd, npage)) )
>> > + break;
>>
>> ... perhaps also this, when you use copy_from_guest() upon access.
>
> This is the one piece of feedback on version 1 of this series that I haven't
> taken the time to address yet. The code is evidently safe, with only a possible
> performance decrease a concern, so I'd like to study it further before removing
> any of the checks rather than delay posting version two of this series.
Hmm, re-posting without all comments addressed is not ideal.
It means extra work for the reviewers (unless you've clearly
marked respective code fragments with some sort of TBD
comment).
Jan
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next prev parent reply other threads:[~2018-12-20 8:29 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 [this message]
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
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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