> -----Original Message----- > From: Max Gurtovoy [mailto:mgurtovoy@xxxxxxxxxx] > Sent: 26 September 2021 10:10 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>; > Leon Romanovsky <leon@xxxxxxxxxx> > Cc: Doug Ledford <dledford@xxxxxxxxxx>; Jason Gunthorpe > <jgg@xxxxxxxxxx>; Yishai Hadas <yishaih@xxxxxxxxxx>; Alex Williamson > <alex.williamson@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; David > S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Kirti > Wankhede <kwankhede@xxxxxxxxxx>; kvm@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; > linux-rdma@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Saeed Mahameed > <saeedm@xxxxxxxxxx>; liulongfang <liulongfang@xxxxxxxxxx> > Subject: Re: [PATCH mlx5-next 2/7] vfio: Add an API to check migration state > transition validity > > > On 9/24/2021 10:44 AM, Shameerali Kolothum Thodi wrote: > > > >> -----Original Message----- > >> From: Max Gurtovoy [mailto:mgurtovoy@xxxxxxxxxx] > >> Sent: 23 September 2021 14:56 > >> To: Leon Romanovsky <leon@xxxxxxxxxx>; Shameerali Kolothum Thodi > >> <shameerali.kolothum.thodi@xxxxxxxxxx> > >> Cc: Doug Ledford <dledford@xxxxxxxxxx>; Jason Gunthorpe > >> <jgg@xxxxxxxxxx>; Yishai Hadas <yishaih@xxxxxxxxxx>; Alex Williamson > >> <alex.williamson@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; > >> David S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski > >> <kuba@xxxxxxxxxx>; Kirti Wankhede <kwankhede@xxxxxxxxxx>; > >> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > >> linux-pci@xxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; > >> netdev@xxxxxxxxxxxxxxx; Saeed Mahameed <saeedm@xxxxxxxxxx> > >> Subject: Re: [PATCH mlx5-next 2/7] vfio: Add an API to check > >> migration state transition validity > >> > >> > >> On 9/23/2021 2:17 PM, Leon Romanovsky wrote: > >>> On Thu, Sep 23, 2021 at 10:33:10AM +0000, Shameerali Kolothum Thodi > >> wrote: > >>>>> -----Original Message----- > >>>>> From: Leon Romanovsky [mailto:leon@xxxxxxxxxx] > >>>>> Sent: 22 September 2021 11:39 > >>>>> To: Doug Ledford <dledford@xxxxxxxxxx>; Jason Gunthorpe > >> <jgg@xxxxxxxxxx> > >>>>> Cc: Yishai Hadas <yishaih@xxxxxxxxxx>; Alex Williamson > >>>>> <alex.williamson@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; > >> David > >>>>> S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; > >>>>> Kirti Wankhede <kwankhede@xxxxxxxxxx>; kvm@xxxxxxxxxxxxxxx; > >>>>> linux-kernel@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; > >>>>> linux-rdma@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Saeed Mahameed > >>>>> <saeedm@xxxxxxxxxx> > >>>>> Subject: [PATCH mlx5-next 2/7] vfio: Add an API to check migration > >>>>> state transition validity > >>>>> > >>>>> From: Yishai Hadas <yishaih@xxxxxxxxxx> > >>>>> > >>>>> Add an API in the core layer to check migration state transition > >>>>> validity as part of a migration flow. > >>>>> > >>>>> The valid transitions follow the expected usage as described in > >>>>> uapi/vfio.h and triggered by QEMU. > >>>>> > >>>>> This ensures that all migration implementations follow a > >>>>> consistent migration state machine. > >>>>> > >>>>> Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx> > >>>>> Reviewed-by: Kirti Wankhede <kwankhede@xxxxxxxxxx> > >>>>> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > >>>>> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx> > >>>>> --- > >>>>> drivers/vfio/vfio.c | 41 > >> +++++++++++++++++++++++++++++++++++++++++ > >>>>> include/linux/vfio.h | 1 + > >>>>> 2 files changed, 42 insertions(+) > >>>>> > >>>>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index > >>>>> 3c034fe14ccb..c3ca33e513c8 100644 > >>>>> --- a/drivers/vfio/vfio.c > >>>>> +++ b/drivers/vfio/vfio.c > >>>>> @@ -1664,6 +1664,47 @@ static int vfio_device_fops_release(struct > >> inode > >>>>> *inode, struct file *filep) > >>>>> return 0; > >>>>> } > >>>>> > >>>>> +/** > >>>>> + * vfio_change_migration_state_allowed - Checks whether a > >>>>> +migration > >> state > >>>>> + * transition is valid. > >>>>> + * @new_state: The new state to move to. > >>>>> + * @old_state: The old state. > >>>>> + * Return: true if the transition is valid. > >>>>> + */ > >>>>> +bool vfio_change_migration_state_allowed(u32 new_state, u32 > >> old_state) > >>>>> +{ > >>>>> + enum { MAX_STATE = VFIO_DEVICE_STATE_RESUMING }; > >>>>> + static const u8 vfio_from_state_table[MAX_STATE + 1][MAX_STATE + > >> 1] = { > >>>>> + [VFIO_DEVICE_STATE_STOP] = { > >>>>> + [VFIO_DEVICE_STATE_RUNNING] = 1, > >>>>> + [VFIO_DEVICE_STATE_RESUMING] = 1, > >>>>> + }, > >>>>> + [VFIO_DEVICE_STATE_RUNNING] = { > >>>>> + [VFIO_DEVICE_STATE_STOP] = 1, > >>>>> + [VFIO_DEVICE_STATE_SAVING] = 1, > >>>>> + [VFIO_DEVICE_STATE_SAVING | > >> VFIO_DEVICE_STATE_RUNNING] > >>>>> = 1, > >>>> Do we need to allow _RESUMING state here or not? As per the "State > >> transitions" > >>>> section from uapi/linux/vfio.h, > >>> It looks like we missed this state transition. > >>> > >>> Thanks > >> I'm not sure this state transition is valid. > >> > >> Kirti, When we would like to move from RUNNING to RESUMING ? > > I guess it depends on what you report as your dev default state. > > > > For HiSilicon ACC migration driver, we set the default to _RUNNING. > > Where do you set it and report it ? Currently, in _open_device() we set the device_state to _RUNNING. I think in your case the default of vmig->vfio_dev_state == 0 (_STOP). > > > > > And when the migration starts, the destination side Qemu, set the > > device state to _RESUMING(vfio_load_state()). > > > > From the documentation, it looks like the assumption on default state > > of the VFIO dev is _RUNNING. > > > > " > > * 001b => Device running, which is the default state " > > > >> Sameerali, can you please re-test and update if you see this transition ? > > Yes. And if I change the default state to _STOP, then the transition > > is from _STOP --> _RESUMING. > > > > But the documentation on State transitions doesn't have _STOP --> > > _RESUMING transition as valid. > > > > Thanks, > > Shameer > > > >> > >>>> " * 4. To start the resuming phase, the device state should be > >>>> transitioned > >> from > >>>> * the _RUNNING to the _RESUMING state." > >>>> > >>>> IIRC, I have seen that transition happening on the destination dev > >>>> while > >> testing the > >>>> HiSilicon ACC dev migration. > >>>> > >>>> Thanks, > >>>> Shameer > >>>> > >>>>> + }, > >>>>> + [VFIO_DEVICE_STATE_SAVING] = { > >>>>> + [VFIO_DEVICE_STATE_STOP] = 1, > >>>>> + [VFIO_DEVICE_STATE_RUNNING] = 1, > >>>>> + }, > >>>>> + [VFIO_DEVICE_STATE_SAVING | VFIO_DEVICE_STATE_RUNNING] > >> = { > >>>>> + [VFIO_DEVICE_STATE_RUNNING] = 1, > >>>>> + [VFIO_DEVICE_STATE_SAVING] = 1, > >>>>> + }, > >>>>> + [VFIO_DEVICE_STATE_RESUMING] = { > >>>>> + [VFIO_DEVICE_STATE_RUNNING] = 1, > >>>>> + [VFIO_DEVICE_STATE_STOP] = 1, > >>>>> + }, > >>>>> + }; > >>>>> + > >>>>> + if (new_state > MAX_STATE || old_state > MAX_STATE) > >>>>> + return false; > >>>>> + > >>>>> + return vfio_from_state_table[old_state][new_state]; > >>>>> +} > >>>>> +EXPORT_SYMBOL_GPL(vfio_change_migration_state_allowed); > >>>>> + > >>>>> static long vfio_device_fops_unl_ioctl(struct file *filep, > >>>>> unsigned int cmd, unsigned long arg) > >>>>> { > >>>>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h index > >>>>> b53a9557884a..e65137a708f1 100644 > >>>>> --- a/include/linux/vfio.h > >>>>> +++ b/include/linux/vfio.h > >>>>> @@ -83,6 +83,7 @@ extern struct vfio_device > >>>>> *vfio_device_get_from_dev(struct device *dev); > >>>>> extern void vfio_device_put(struct vfio_device *device); > >>>>> > >>>>> int vfio_assign_device_set(struct vfio_device *device, void > >>>>> *set_id); > >>>>> +bool vfio_change_migration_state_allowed(u32 new_state, u32 > >> old_state); > >>>>> /* events for the backend driver notify callback */ > >>>>> enum vfio_iommu_notify_type { > >>>>> -- > >>>>> 2.31.1
