On Tue, Jul 20, 2021 at 03:27:00PM +0300, Max Gurtovoy wrote:
> On 7/20/2021 6:02 AM, Jason Wang wrote:
> > 在 2021/7/19 下午8:43, Stefan Hajnoczi 写道:
> > > On Fri, Jul 16, 2021 at 10:03:17AM +0800, Jason Wang wrote:
> > > > 在 2021/7/15 下午6:01, Stefan Hajnoczi 写道:
> > > > > On Thu, Jul 15, 2021 at 09:35:13AM +0800, Jason Wang wrote:
> > > > > > 在 2021/7/14 下午11:07, Stefan Hajnoczi 写道:
> > > > > > > On Wed, Jul 14, 2021 at 06:29:28PM +0800, Jason Wang wrote:
> > > > > > > > 在 2021/7/14 下午5:53, Stefan Hajnoczi 写道:
> > > > > > > > > On Tue, Jul 13, 2021 at 08:16:35PM +0800, Jason Wang wrote:
> > > > > > > > > > 在 2021/7/13 下午6:00, Stefan Hajnoczi 写道:
> > > > > > > > > > > On Tue, Jul 13, 2021 at 11:27:03AM +0800, Jason Wang wrote:
> > > > > > > > > > > > 在 2021/7/12 下午5:57, Stefan Hajnoczi 写道:
> > > > > > > > > > > > > On Mon, Jul 12, 2021 at 12:00:39PM +0800, Jason Wang wrote:
> > > > > > > > > > > > > > 在 2021/7/11 上午4:36, Michael S. Tsirkin 写道:
> > > > > > > > > > > > > > > On Fri, Jul 09, 2021
> > > > > > > > > > > > > > > at 07:23:33PM +0200,
> > > > > > > > > > > > > > > Eugenio Perez Martin
> > > > > > > > > > > > > > > wrote:
> > > > > > > That's
> > > > > > > basically the difference between the vhost/vDPA's
> > > > > > > selective passthrough
> > > > > > > approach and VFIO's full passthrough approach.
> > > > > > We can't do VFIO full pasthrough for migration anyway,
> > > > > > some kind of mdev is
> > > > > > required but it's duplicated with the current vp_vdpa driver.
> > > > > I'm not sure that's true. Generic VFIO PCI migration can probably be
> > > > > achieved without mdev:
> > > > > 1. Define a migration PCI Capability that indicates support for
> > > > >      VFIO_REGION_TYPE_MIGRATION. This allows the PCI device
> > > > > to implement
> > > > >      the migration interface in hardware instead of an mdev driver.
> > > > 
> > > > So I think it still depend on the driver to implement migrate
> > > > state which is
> > > > vendor specific.
> > > The current VFIO migration interface depends on a device-specific
> > > software mdev driver but here I'm showing that the physical device can
> > > implement the migration interface so that no device-specific driver code
> > > is needed.
> > 
> > 
> > This is not what I read from the patch:
> > 
> >  * device_state: (read/write)
> >  *      - The user application writes to this field to inform the vendor
> > driver
> >  *        about the device state to be transitioned to.
> >  *      - The vendor driver should take the necessary actions to change
> > the
> >  *        device state. After successful transition to a given state, the
> >  *        vendor driver should return success on write(device_state,
> > state)
> >  *        system call. If the device state transition fails, the vendor
> > driver
> >  *        should return an appropriate -errno for the fault condition.
> > 
> > Vendor driver need to mediate between the uAPI and the actual device.
> 
> We're building an infrastructure for VFIO PCI devices in the last few
> months.
> 
> It should be merged hopefully to kernel 5.15.

Do you have links to patch series or a brief description of the VFIO API
features that are on the roadmap?

> 
> > 
> > 
> > > 
> > > > Note that it's just an uAPI definition not something defined in the PCI
> > > > spec.
> > > Yes, that's why I mentioned Changpeng Liu's idea to turn the uAPI into a
> > > standard PCI Capability to eliminate the need for device-specific
> > > drivers.
> > 
> > 
> > Ok.
> > 
> > 
> > > 
> > > > Out of curiosity, the patch is merged without any real users in
> > > > the Linux.
> > > > This is very bad since we lose the change to audit the whole design.
> > > I agree. It would have helped to have a complete vision for how live
> > > migration should work along with demos. I don't see any migration code
> > > in samples/vfio-mdev/ :(.
> > 
> > 
> > Right.
> 
> Creating a standard is not related to Linux nor VFIO.
> 
> With the proposal that I've sent, we can develop a migration driver and
> virtio device that will support it (NVIDIA virtio-blk SNAP device).
> 
> And you can build live migration support in virtio_vdpa driver (if VDPA
> migration protocol will be implemented).

I guess "VDPA migration protocol" is not referring to Jason's proposal
but instead to a new vDPA interface that adds the migration interface
from you proposal to vDPA?

Stefan