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Re: [PATCH v26 05/17] vfio: Add VM state change handler to know state of
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM |
Date: |
Tue, 29 Sep 2020 12:03:12 +0100 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
* Cornelia Huck (cohuck@redhat.com) wrote:
> On Wed, 23 Sep 2020 04:54:07 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>
> > VM state change handler gets called on change in VM's state. This is used
> > to set
> > VFIO device state to _RUNNING.
> >
> > Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> > Reviewed-by: Neo Jia <cjia@nvidia.com>
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > hw/vfio/migration.c | 136
> > ++++++++++++++++++++++++++++++++++++++++++
> > hw/vfio/trace-events | 3 +-
> > include/hw/vfio/vfio-common.h | 4 ++
> > 3 files changed, 142 insertions(+), 1 deletion(-)
> >
>
> (...)
>
> > +static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
> > + uint32_t value)
>
> I think I've mentioned that before, but this function could really
> benefit from a comment what mask and value mean.
>
> > +{
> > + VFIOMigration *migration = vbasedev->migration;
> > + VFIORegion *region = &migration->region;
> > + off_t dev_state_off = region->fd_offset +
> > + offsetof(struct vfio_device_migration_info,
> > device_state);
> > + uint32_t device_state;
> > + int ret;
> > +
> > + ret = vfio_mig_read(vbasedev, &device_state, sizeof(device_state),
> > + dev_state_off);
> > + if (ret < 0) {
> > + return ret;
> > + }
> > +
> > + device_state = (device_state & mask) | value;
> > +
> > + if (!VFIO_DEVICE_STATE_VALID(device_state)) {
> > + return -EINVAL;
> > + }
> > +
> > + ret = vfio_mig_write(vbasedev, &device_state, sizeof(device_state),
> > + dev_state_off);
> > + if (ret < 0) {
> > + ret = vfio_mig_read(vbasedev, &device_state, sizeof(device_state),
> > + dev_state_off);
> > + if (ret < 0) {
> > + return ret;
> > + }
> > +
> > + if (VFIO_DEVICE_STATE_IS_ERROR(device_state)) {
> > + hw_error("%s: Device is in error state 0x%x",
> > + vbasedev->name, device_state);
> > + return -EFAULT;
>
> Is -EFAULT a good return value here? Maybe -EIO?
>
> > + }
> > + }
> > +
> > + vbasedev->device_state = device_state;
> > + trace_vfio_migration_set_state(vbasedev->name, device_state);
> > + return 0;
> > +}
> > +
> > +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
> - if _RESUMING was not set, clear everything previously set
> This would really benefit from a comment (or am I the only one
> struggling here?)
>
> > + }
> > + } else {
> > + mask = ~VFIO_DEVICE_STATE_RUNNING;
> > + }
> > +
> > + ret = vfio_migration_set_state(vbasedev, mask, value);
> > + if (ret) {
> > + /*
> > + * vm_state_notify() doesn't support reporting failure. If such
> > + * error reporting support added in furure, migration should be
> > + * aborted.
>
>
> "We should abort the migration in this case, but vm_state_notify()
> currently does not support reporting failures."
>
> ?
>
> Can/should we mark the failing device in some way?
I think you can call qemu_file_set_error on the migration stream to
force an error.
Dave
> > + */
> > + error_report("%s: Failed to set device state 0x%x",
> > + vbasedev->name, value & mask);
> > + }
> > + vbasedev->vm_running = running;
> > + trace_vfio_vmstate_change(vbasedev->name, running,
> > RunState_str(state),
> > + value & mask);
> > + }
> > +}
> > +
> > static int vfio_migration_init(VFIODevice *vbasedev,
> > struct vfio_region_info *info)
> > {
>
> (...)
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- [PATCH v26 02/17] vfio: Add vfio_get_object callback to VFIODeviceOps, (continued)
- [PATCH v26 02/17] vfio: Add vfio_get_object callback to VFIODeviceOps, Kirti Wankhede, 2020/09/22
- [PATCH v26 03/17] vfio: Add save and load functions for VFIO PCI devices, Kirti Wankhede, 2020/09/22
- [PATCH v26 04/17] vfio: Add migration region initialization and finalize function, Kirti Wankhede, 2020/09/22
- [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM, Kirti Wankhede, 2020/09/22
- [PATCH v26 06/17] vfio: Add migration state change notifier, Kirti Wankhede, 2020/09/22
- [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device, Kirti Wankhede, 2020/09/22
- [PATCH v26 08/17] vfio: Add save state functions to SaveVMHandlers, Kirti Wankhede, 2020/09/22