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Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle
From: |
Halil Pasic |
Subject: |
Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request |
Date: |
Wed, 17 May 2017 15:04:15 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
On 05/17/2017 01:10 PM, Cornelia Huck wrote:
> On Wed, 17 May 2017 12:33:20 +0200
> Halil Pasic <address@hidden> wrote:
>
>> On 05/17/2017 12:13 PM, Gonglei (Arei) wrote:
>>>>
>>>> On 05/17/2017 11:12 AM, Gonglei (Arei) wrote:
>>>>>>>> By the way, I'm having a hard time understing how is the requirement
>>>> form
>>>>>>>>
>>>>>>
>>>> http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-260
>>>>>>>> 004
>>>>>>>> (2.4.4 Message Framing) satisfied by this code. Could you explain this
>>>>>>>> to me please?
>>>>>>>>
>>>>>>> Sorry for my bad English,
>>>>>>> I don't know which normative formulation the code violates?
>>>>>> I'm not sure it's actually violated, but I'm concerned about the
>>>>>> following
>>>>>> normative statement: "The device MUST NOT make assumptions about the
>>>>>> particular
>>>>>> arrangement of descriptors. The device MAY have a reasonable limit of
>>>>>> descriptors it will allow in a chain."
>>>>>>
>>>>>> Please also read the explanatory part I've linked, because the normative
>>>>>> statement is pretty abstract.
>>>>>>
>>>>>> In my understanding, the spec says, that e.g. the virti-crypto device
>>>>>> should not fail if a single request is split up into let's say two chunks
>>>>>> and transmitted by the means of two top level descriptors.
>>>>>>
>>>>>> Do you agree with my reading of the spec?
>>>>>>
>>>>> Yes, I agree. But what's the relationship about the request here?
>>>>> We don't assume the request have to use one desc entity, it can
>>>>> use scatter-gather list for one request header.
>>>>> The device can cover the situation in the QEMU.
>>>>>
>>>>>> What does the virtio-crypto device do if it encounters such a situation?
>>>>>>
>>>>> This isn't a problem. Pls see blow code segment:
>>>>>
>>>>> virtio_crypto_handle_request()
>>>>> {...
>>>>> if (unlikely(iov_to_buf(out_iov, out_num, 0, &req, sizeof(req))
>>>>> != sizeof(req))) {
>>>>> virtio_error(vdev, "virtio-crypto request outhdr too short");
>>>>> return -1;
>>>>> }
>>>>> iov_discard_front(&out_iov, &out_num, sizeof(req));
>>>>> ...
>>>>>
>>>>
>>>> Thats exactly what worries me. I see a call to virtio_error there...
>>>>
>>>>
>>>> void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt,
>>>> ...)
>>>> {
>>>> va_list ap;
>>>>
>>>> va_start(ap, fmt);
>>>> error_vreport(fmt, ap);
>>>> va_end(ap);
>>>>
>>>> vdev->broken = true;
>>>>
>>>> if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
>>>> virtio_set_status(vdev, vdev->status |
>>>> VIRTIO_CONFIG_S_NEEDS_RESET);
>>>> virtio_notify_config(vdev);
>>>> }
>>>> }
>>>>
>>>> This however seems to make the device 'broken'. Or am I missing something?
>>>>
>>> Yes, if the parse process failed, the device will broke.
>>> But This is a exception scenario IMHO, which is the same situation
>>> with other virtio devices.
>>
>> I know that virtio-blk does the same. I'm not sure my reading of the
>> spec is correct. Maybe Stefan, Michael or Connie can clarify this
>> for us!
>
> The spec says for NEEDS_RESET:
>
> "Indicates that the device has experienced an error from which it can't
> recover."
>
> For me, this means:
> - If this is something that might happen in the normal course of events
> and there's a good recovery path, just recover.
> - Else, use virtio_error() and require the driver to recover via reset.
>
> If the driver is sending requests in an unexpected format, I'd use
> virtio_error(). The format needs to be properly described, though.
>
All-clear, my bad. After re-reading the spec and virtio_pop I have
realized that virtio_pop pops full descriptor chains. These however
correspond to single requests. Thus at the given point the full request
has to be placed into the queue. Sorry!
>>
>> By the way for virtio-blk the current handling was introduced by
>> commit 20ea686a0 (by Greg Kurz), but before we were failing even
>> harder.
>>
>> Regards,
>> Halil
>>
>>>
>>> Stefan introduced the virtio_error().
>>>
>>> Thanks,
>>> -Gonglei
>>>
>
>
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, (continued)
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/12
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Gonglei (Arei), 2017/05/12
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/15
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Gonglei (Arei), 2017/05/15
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/16
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Gonglei (Arei), 2017/05/17
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/17
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Gonglei (Arei), 2017/05/17
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/17
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Cornelia Huck, 2017/05/17
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request,
Halil Pasic <=
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/18
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Gonglei (Arei), 2017/05/18
- Re: [Qemu-devel] [RFC v1 6/9] virtio-crypto: rework virtio_crypto_handle_request, Halil Pasic, 2017/05/29
- [Qemu-devel] [RFC v1 5/9] virtio-crypto: update header file, Gonglei, 2017/05/08
- [Qemu-devel] [RFC v1 3/9] cryptodev: add missing op_code for symmertric crypto, Gonglei, 2017/05/08
- [Qemu-devel] [RFC v1 9/9] qtest: emulate virtio crypto as a legacy device for experiment, Gonglei, 2017/05/08
- [Qemu-devel] [RFC v1 8/9] virtio-crypto: add host feature bits support, Gonglei, 2017/05/08