From: Razvan Cojocaru <rcojocaru@bitdefender.com>
To: "Tamas K Lengyel" <tamas@tklengyel.com>,
"Roger Pau Monné" <roger.pau@citrix.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>,
Christopher Clark <christopher.w.clark@gmail.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>,
Jan Beulich <JBeulich@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>,
eric chanudet <eric.chanudet@gmail.com>
Subject: Re: [PATCH 13/25] argo: implement the register op
Date: Wed, 9 Jan 2019 18:23:29 +0200 [thread overview]
Message-ID: <7c74a02d-e315-2c77-3506-9408b9e5050f@bitdefender.com> (raw)
In-Reply-To: <CABfawhmfhYkHreJ3A4xnmhJjW3581Zt0L5-Vsswz93ZZTMrFQw@mail.gmail.com>
On 1/9/19 6:15 PM, Tamas K Lengyel wrote:
> On Mon, Jan 7, 2019 at 2:01 AM Roger Pau Monné <roger.pau@citrix.com> wrote:
>>
>> Adding the introspection guys.
>>
>> On Fri, Jan 04, 2019 at 08:47:04AM -0700, Jan Beulich wrote:
>>>>>> On 04.01.19 at 16:35, <roger.pau@citrix.com> wrote:
>>>> On Fri, Jan 04, 2019 at 06:22:19AM -0700, Jan Beulich wrote:
>>>>>>>> On 04.01.19 at 09:57, <roger.pau@citrix.com> wrote:
>>>>>> On Fri, Dec 21, 2018 at 03:05:03PM -0800, Christopher Clark wrote:
>>>>>>> On Thu, Dec 20, 2018 at 4:52 AM Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>>>>>>
>>>>>>>> On Wed, Dec 19, 2018 at 09:41:59PM -0800, Christopher Clark wrote:
>>>>>>>>> On Wed, Dec 12, 2018 at 8:48 AM Roger Pau Monné <roger.pau@citrix.com>
>>>> wrote:
>>>>>>>>>>
>>>>>>>>>> On Fri, Nov 30, 2018 at 05:32:52PM -0800, Christopher Clark wrote:
>>>>>>>> Then I wonder why you need such check in any case if the code can
>>>>>>>> handle such cases, the more than the check itself is racy.
>>>>>>>
>>>>>>> OK, so at the root of the question here is: does it matter what the p2m
>>>>>>> type of the memory is at these points:
>>>>>>>
>>>>>>> 1) when the gfn is translated to mfn, at the time of ring registration
>>>>>>
>>>>>> This is the important check, because that's where you should take a
>>>>>> reference to the page. In this case you should check that the page is
>>>>>> of ram_rw type.
>>>>>>
>>>>>>> 2) when the hypervisor writes into guest memory:
>>>>>>> - where the tx_ptr index is initialized in the register op
>>>>>>> - where ringbuf data is written in sendv
>>>>>>> - where ring description data is written in notify
>>>>>>
>>>>>> As long as you keep a reference to the pages that are part of the ring
>>>>>> you don't need to do any checks when writing/reading from them. If the
>>>>>> guest messes up it's p2m and does change the gfn -> mfn mappings for
>>>>>> pages that are part of the ring that's the guest problem, the
>>>>>> hypervisor still has a reference to those pages so they won't be
>>>>>> reused.
>>>>>
>>>>> For use cases like introspection this may not be fully correct,
>>>>> but it may also be that my understanding there isn't fully
>>>>> correct. If introspection agents care about _any_ writes to
>>>>> a page, hypervisor ones (which in most cases are merely
>>>>> writes on behalf of the guest) might matter as well. I think
>>>>> to decide whether page accesses need to be accompanied
>>>>> by any checks (and if so, which ones) one needs to
>>>>> - establish what p2m type transitions are possible for a
>>>>> given page,
>>>>> - verify what restrictions may occur "behind the back" of
>>>>> the entity wanting to do the accesses,
>>>>> - explore whether doing the extra checking at p2m type
>>>>> change time wouldn't be better than at the time of access.
>>>>
>>>> Maybe this is use-case is different, but how does introspection handle
>>>> accesses to the shared info page or the runstate info for example?
>>>>
>>>> I would consider argo to be the same in this regard.
>>>
>>> Not exactly: The shared info page is special in any event. For
>>> runstate info (and alike - there's also struct vcpu_time_info)
>>> I'd question correctness of the current handling. If that's
>>> wrong already, I'd prefer if the issue wasn't spread.
>>
>> There are also grants, which when used together with another guest on
>> the same host could allow to bypass introspection AFAICT? (unless
>> there's some policy applied that limit grant sharing to trusted
>> domains)
>>
>> TBH I'm not sure how to handle hypoervisor accesses with
>> introspection. My knowledge of introspection is fairly limited, but
>> it pauses the guest and sends a notification to an in guest agent. I'm
>> not sure this is applicable to hypervisor writes, since it's not
>> possible to pause hypervisor execution and wait for a response from a
>> guest agent.
>>
>
> Introspection applications only care about memory accesses performed
> by the guest. Hypervisor accesses to monitored pages are not included
> when monitoring - it is actually a feature when using the emulator in
> Xen to continue guest execution because the hypervisor ignores EPT
> memory permissions that trip the guest for introspection. So having
> the hypervisor access memory or a grant-shared page being accessed in
> another domain are not a problem for introspection.
Indeed, that's how it goes.
Thanks,
Razvan
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next prev parent reply other threads:[~2019-01-09 16:23 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 [this message]
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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