[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [virtio-comment] Re: [virtio-dev] Re: [virtio-comment] Re: [VIRTIO PCI PATCH v5 1/1] transport-pci: Add freeze_mode to virtio_pci_common_cfg
Hi Lingshan,
On 2023/9/20 14:58, Zhu, Lingshan wrote:
>
>
> On 9/20/2023 2:33 PM, Chen, Jiqian wrote:
>> Hi Lingshan,
>>
>> On 2023/9/20 13:59, Zhu, Lingshan wrote:
>>>
>>> On 9/19/2023 8:31 PM, Michael S. Tsirkin wrote:
>>>> On Tue, Sep 19, 2023 at 07:42:42PM +0800, Jiqian Chen wrote:
>>>>> When guest vm does S3, Qemu will reset and clear some things of virtio
>>>>> devices, but guest can't aware that, so that may cause some problems.
>>>>> For excample, Qemu calls virtio_reset->virtio_gpu_gl_reset when guest
>>>>> resume, that function will destroy render resources of virtio-gpu. As
>>>>> a result, after guest resume, the display can't come back and we only
>>>>> saw a black screen. Due to guest can't re-create all the resources, so
>>>>> we need to let Qemu not to destroy them when S3.
>>>>>
>>>>> For above purpose, we need a mechanism that allows guests and QEMU to
>>>>> negotiate their reset behavior. So this patch add a new parameter
>>>>> named freeze_mode to struct virtio_pci_common_cfg. And when guest
>>>>> suspends, it can write freeze_mode to be FREEZE_S3, and then virtio
>>>>> devices can change their reset behavior on Qemu side according to
>>>>> freeze_mode. What's more, freeze_mode can be used for all virtio
>>>>> devices to affect the behavior of Qemu, not just virtio gpu device.
>>> Hi Jiqian,
>>>
>>> Have you seen this series: [PATCH 0/5] virtio: introduce SUSPEND bit and vq state
>>> 3f4cbf84-010c-cffa-0b70-33c449b5561b@intel.com/T/">https://lore.kernel.org/all/3f4cbf84-010c-cffa-0b70-33c449b5561b@intel.com/T/
>>>
>>> We introduced a bit in the device status SUSPEND, when VIRTIO_F_SUSPEND is
>>> negotiated, the driver can set SUSPEND in the device status to suspend the
>>> device.
>>>
>>> When SUSPEND, the device should pause its operations and preserve its configurations
>>> in its configuration space.
>>>
>>> The driver re-write DRIVER_OK to clear SUSPEND, so the device resumes running.
>>>
>>> This is originally to serve live migration, but I think it can also meet your needs.
>> I noticed your series, but I am not sure they are also meet my needs.
>> If driver write 0 to reset device, can the SUSPEND bit be cleared? (pci_pm_resume->virtio_pci_restore->virtio_device_restore->virtio_reset_device)
> if the driver writes 0, it resets all virtio functionalities. So SUSPEND is cleared.
Then your patches are not meet my needs. In my scene, it needs to keep the SUSPEND bit util the resume process is complete.
Because in my virtio-gpu scene, when guest resume, it call virtio_reset_device to clear all device status bits, and then reset virtio-gpu in Qemu, and then destroy render resources, I don't want the resources are destroyed during the resume process. So, I add freeze_mode to tell Qemu that guest is doing S3 and resources need to be kept.
> device reset can also be used to recover the device from fatal errors, so it should reset everything in virtio.
>> If SUSPEND is cleared, then during the reset process in Qemu, I can't judge if the reset request is from guest restore process or not, and then I can't change the reset behavior.
> I think when enter S3, the hypervisor/driver should set SUSPEND to the device. And when resume from S3, the hypervisor/driver should
> re-write DRIVER_OK to clear SUSPEND, then the device resume running.
>> Can you send me your patch link on kernel and qemu side? I will take a deep look.
> There are no patches for qemu/kernel yet, spec first.
>>
>>> Thanks,
>>> Zhu Lingshan
>>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>>>> ---
>>>>> ÂÂ transport-pci.tex | 7 +++++++
>>>>> ÂÂ 1 file changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/transport-pci.tex b/transport-pci.tex
>>>>> index a5c6719..2543536 100644
>>>>> --- a/transport-pci.tex
>>>>> +++ b/transport-pci.tex
>>>>> @@ -319,6 +319,7 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
>>>>> ÂÂÂÂÂÂÂÂÂÂ le64 queue_desc;ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* read-write */
>>>>> ÂÂÂÂÂÂÂÂÂÂ le64 queue_driver;ÂÂÂÂÂÂÂÂÂÂÂÂÂ /* read-write */
>>>>> ÂÂÂÂÂÂÂÂÂÂ le64 queue_device;ÂÂÂÂÂÂÂÂÂÂÂÂÂ /* read-write */
>>>>> +ÂÂÂÂÂÂÂ le16 freeze_mode;ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* read-write */
>>>>> ÂÂÂÂÂÂÂÂÂÂ le16 queue_notif_config_data;ÂÂ /* read-only for driver */
>>>>> ÂÂÂÂÂÂÂÂÂÂ le16 queue_reset;ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* read-write */
>>>>>
>>>> we can't add fields in the middle of the structure like this -
>>>> offset of queue_notif_config_data and queue_reset changes.
>>>>
>>>> ÂÂ
>>>>> @@ -393,6 +394,12 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
>>>>> ÂÂ \item[\field{queue_device}]
>>>>>  The driver writes the physical address of Device Area here. See section \ref{sec:Basic Facilities of a Virtio Device / Virtqueues}.
>>>>> ÂÂ +\item[\field{freeze_mode}]
>>>>> +ÂÂÂÂÂÂÂ The driver writes this to set the freeze mode of virtio pci.
>>>>> +ÂÂÂÂÂÂÂ VIRTIO_PCI_FREEZE_MODE_UNFREEZE - virtio-pci is running;
>>>>> +ÂÂÂÂÂÂÂ VIRTIO_PCI_FREEZE_MODE_FREEZE_S3 - guest vm is doing S3, and virtio-pci enters S3 suspension;
>>>>> +ÂÂÂÂÂÂÂ Other values are reserved for future use, like S4, etc.
>>>>> +
>>>> we need to specify these values then.
>>>>
>>>> we also need
>>>> - feature bit to detect support for S3
>>>> - conformance statements documenting behavious under S3
>>>>
>>>>
>>>>> ÂÂ \item[\field{queue_notif_config_data}]
>>>>> ÂÂÂÂÂÂÂÂÂÂ This field exists only if VIRTIO_F_NOTIF_CONFIG_DATA has been negotiated.
>>>>> ÂÂÂÂÂÂÂÂÂÂ The driver will use this value when driver sends available buffer
>>>>> --Â
>>>>> 2.34.1
>>>> This publicly archived list offers a means to provide input to the
>>>> OASIS Virtual I/O Device (VIRTIO) TC.
>>>>
>>>> In order to verify user consent to the Feedback License terms and
>>>> to minimize spam in the list archive, subscription is required
>>>> before posting.
>>>>
>>>> Subscribe: virtio-comment-subscribe@lists.oasis-open.org
>>>> Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org
>>>> List help: virtio-comment-help@lists.oasis-open.org
>>>> List archive: https://lists.oasis-open.org/archives/virtio-comment/
>>>> Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf
>>>> List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists
>>>> Committee: https://www.oasis-open.org/committees/virtio/
>>>> Join OASIS: https://www.oasis-open.org/join/
>>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org
>>> For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
>>>
>
>
> This publicly archived list offers a means to provide input to the
> OASIS Virtual I/O Device (VIRTIO) TC.
>
> In order to verify user consent to the Feedback License terms and
> to minimize spam in the list archive, subscription is required
> before posting.
>
> Subscribe: virtio-comment-subscribe@lists.oasis-open.org
> Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org
> List help: virtio-comment-help@lists.oasis-open.org
> List archive: https://lists.oasis-open.org/archives/virtio-comment/
> Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf
> List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists
> Committee: https://www.oasis-open.org/committees/virtio/
> Join OASIS: https://www.oasis-open.org/join/
>
--
Best regards,
Jiqian Chen.
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]