From: Cornelia Huck <cohuck@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: cjia@nvidia.com, aik@ozlabs.ru, Zhengxiao.zx@alibaba-inc.com,
shuangtai.tst@alibaba-inc.com, qemu-devel@nongnu.org,
peterx@redhat.com, eauger@redhat.com, yi.l.liu@intel.com,
quintela@redhat.com, ziye.yang@intel.com, armbru@redhat.com,
mlevitsk@redhat.com, pasic@linux.ibm.com, felipe@nutanix.com,
zhi.a.wang@intel.com, kevin.tian@intel.com, yan.y.zhao@intel.com,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
alex.williamson@redhat.com, changpeng.liu@intel.com,
eskultet@redhat.com, Ken.Xue@amd.com,
jonathan.davies@nutanix.com, pbonzini@redhat.com
Subject: Re: [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM
Date: Thu, 22 Oct 2020 09:51:25 +0200 [thread overview]
Message-ID: <20201022095125.60319084.cohuck@redhat.com> (raw)
In-Reply-To: <245abdf6-245d-5f88-e04b-35fad763560c@nvidia.com>
On Wed, 21 Oct 2020 11:03:23 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:
> On 10/20/2020 4:21 PM, Cornelia Huck wrote:
> > On Sun, 18 Oct 2020 01:54:56 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >
> >> On 9/29/2020 4:33 PM, Dr. David Alan Gilbert wrote:
> >>> * Cornelia Huck (cohuck@redhat.com) wrote:
> >>>> On Wed, 23 Sep 2020 04:54:07 +0530
> >>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >>>>> +static void vfio_vmstate_change(void *opaque, int running, RunState state)
> >>>>> +{
> >>>>> + VFIODevice *vbasedev = opaque;
> >>>>> +
> >>>>> + if ((vbasedev->vm_running != running)) {
> >>>>> + int ret;
> >>>>> + uint32_t value = 0, mask = 0;
> >>>>> +
> >>>>> + if (running) {
> >>>>> + value = VFIO_DEVICE_STATE_RUNNING;
> >>>>> + if (vbasedev->device_state & VFIO_DEVICE_STATE_RESUMING) {
> >>>>> + mask = ~VFIO_DEVICE_STATE_RESUMING;
> >>>>
> >>>> I've been staring at this for some time and I think that the desired
> >>>> result is
> >>>> - set _RUNNING
> >>>> - if _RESUMING was set, clear it, but leave the other bits intact
> >>
> >> Upto here, you're correct.
> >>
> >>>> - if _RESUMING was not set, clear everything previously set
> >>>> This would really benefit from a comment (or am I the only one
> >>>> struggling here?)
> >>>>
> >>
> >> Here mask should be ~0. Correcting it.
> >
> > Hm, now I'm confused. With value == _RUNNING, ~_RUNNING and ~0 as mask
> > should be equivalent, shouldn't they?
> >
>
> I too got confused after reading your comment.
> Lets walk through the device states and transitions can happen here:
>
> if running
> - device state could be either _SAVING or _RESUMING or _STOP. Both
> _SAVING and _RESUMING can't be set at a time, that is the error state.
> _STOP means 0.
> - Transition from _SAVING to _RUNNING can happen if there is migration
> failure, in that case we have to clear _SAVING
> - Transition from _RESUMING to _RUNNING can happen on resuming and we
> have to clear _RESUMING.
> - In both the above cases, we have to set _RUNNING and clear rest 2 bits.
> Then:
> mask = ~VFIO_DEVICE_STATE_MASK;
> value = VFIO_DEVICE_STATE_RUNNING;
ok
>
> if !running
> - device state could be either _RUNNING or _SAVING|_RUNNING. Here we
> have to reset running bit.
> Then:
> mask = ~VFIO_DEVICE_STATE_RUNNING;
> value = 0;
ok
>
> I'll add comment in the code above.
That will help.
I'm a bit worried though that all that reasoning which flags are set or
cleared when is quite complex, and it's easy to make mistakes.
Can we model this as a FSM, where an event (running state changes)
transitions the device state from one state to another? I (personally)
find FSMs easier to comprehend, but I'm not sure whether that change
would be too invasive. If others can parse the state changes with that
mask/value interface, I won't object to it.
>
>
> >>
> >>
> >>>>> + }
> >>>>> + } else {
> >>>>> + mask = ~VFIO_DEVICE_STATE_RUNNING;
> >>>>> + }
next prev parent reply other threads:[~2020-10-22 7:52 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 23:24 [PATCH QEMU v25 00/17] Add migration support for VFIO devices Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 01/17] vfio: Add function to unmap VFIO region Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 02/17] vfio: Add vfio_get_object callback to VFIODeviceOps Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 03/17] vfio: Add save and load functions for VFIO PCI devices Kirti Wankhede
2020-09-23 6:38 ` Zenghui Yu
2020-09-24 22:49 ` Alex Williamson
2020-10-21 9:30 ` Zenghui Yu
2020-10-21 19:03 ` Alex Williamson
2020-09-22 23:24 ` [PATCH v26 04/17] vfio: Add migration region initialization and finalize function Kirti Wankhede
2020-09-24 14:08 ` Cornelia Huck
2020-10-17 20:14 ` Kirti Wankhede
2020-09-25 20:20 ` Alex Williamson
2020-09-28 9:39 ` Cornelia Huck
2020-10-17 20:17 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM Kirti Wankhede
2020-09-24 15:02 ` Cornelia Huck
2020-09-29 11:03 ` Dr. David Alan Gilbert
2020-10-17 20:24 ` Kirti Wankhede
2020-10-20 10:51 ` Cornelia Huck
2020-10-21 5:33 ` Kirti Wankhede
2020-10-22 7:51 ` Cornelia Huck [this message]
2020-10-22 15:42 ` Kirti Wankhede
2020-10-22 15:49 ` Cornelia Huck
2020-09-25 20:20 ` Alex Williamson
2020-10-17 20:30 ` Kirti Wankhede
2020-10-17 23:44 ` Alex Williamson
2020-10-18 17:43 ` Kirti Wankhede
2020-10-19 17:51 ` Alex Williamson
2020-10-20 10:23 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 06/17] vfio: Add migration state change notifier Kirti Wankhede
2020-09-25 20:20 ` Alex Williamson
2020-10-17 20:35 ` Kirti Wankhede
2020-10-19 17:57 ` Alex Williamson
2020-10-20 10:55 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device Kirti Wankhede
2020-09-24 15:15 ` Philippe Mathieu-Daudé
2020-09-29 10:19 ` Dr. David Alan Gilbert
2020-10-17 20:36 ` Kirti Wankhede
2020-09-25 11:53 ` Cornelia Huck
2020-10-18 20:55 ` Kirti Wankhede
2020-10-20 15:51 ` Cornelia Huck
2020-09-25 20:20 ` Alex Williamson
2020-10-18 17:40 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 08/17] vfio: Add save state functions to SaveVMHandlers Kirti Wankhede
2020-09-23 11:42 ` Wang, Zhi A
2020-10-21 14:30 ` Kirti Wankhede
2020-09-25 21:02 ` Alex Williamson
2020-10-18 18:00 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 09/17] vfio: Add load " Kirti Wankhede
2020-10-01 10:07 ` Cornelia Huck
2020-10-18 20:47 ` Kirti Wankhede
2020-10-20 16:25 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 10/17] memory: Set DIRTY_MEMORY_MIGRATION when IOMMU is enabled Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 11/17] vfio: Get migration capability flags for container Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 12/17] vfio: Add function to start and stop dirty pages tracking Kirti Wankhede
2020-09-25 21:55 ` Alex Williamson
2020-10-18 20:52 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 13/17] vfio: create mapped iova list when vIOMMU is enabled Kirti Wankhede
2020-09-25 22:23 ` Alex Williamson
2020-10-19 6:01 ` Kirti Wankhede
2020-10-19 17:24 ` Alex Williamson
2020-10-19 19:15 ` Kirti Wankhede
2020-10-19 20:07 ` Alex Williamson
2020-09-22 23:24 ` [PATCH v26 14/17] vfio: Add vfio_listener_log_sync to mark dirty pages Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 15/17] vfio: Add ioctl to get dirty pages bitmap during dma unmap Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 16/17] vfio: Make vfio-pci device migration capable Kirti Wankhede
2020-09-25 12:17 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 17/17] qapi: Add VFIO devices migration stats in Migration stats Kirti Wankhede
2020-09-24 15:14 ` Eric Blake
2020-09-25 22:55 ` Alex Williamson
2020-09-29 10:40 ` Dr. David Alan Gilbert
2020-09-23 7:06 ` [PATCH QEMU v25 00/17] Add migration support for VFIO devices Zenghui Yu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201022095125.60319084.cohuck@redhat.com \
--to=cohuck@redhat.com \
--cc=Ken.Xue@amd.com \
--cc=Zhengxiao.zx@alibaba-inc.com \
--cc=aik@ozlabs.ru \
--cc=alex.williamson@redhat.com \
--cc=armbru@redhat.com \
--cc=changpeng.liu@intel.com \
--cc=cjia@nvidia.com \
--cc=dgilbert@redhat.com \
--cc=eauger@redhat.com \
--cc=eskultet@redhat.com \
--cc=felipe@nutanix.com \
--cc=jonathan.davies@nutanix.com \
--cc=kevin.tian@intel.com \
--cc=kwankhede@nvidia.com \
--cc=mlevitsk@redhat.com \
--cc=pasic@linux.ibm.com \
--cc=pbonzini@redhat.com \
--cc=peterx@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=quintela@redhat.com \
--cc=shuangtai.tst@alibaba-inc.com \
--cc=yan.y.zhao@intel.com \
--cc=yi.l.liu@intel.com \
--cc=zhi.a.wang@intel.com \
--cc=ziye.yang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).