lkml.org 
[lkml]   [2021]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC] /dev/ioasid uAPI proposal
    On Fri, Jun 04, 2021 at 06:37:26AM +0000, Tian, Kevin wrote:
    > > From: Jason Gunthorpe
    > > Sent: Thursday, June 3, 2021 9:05 PM
    > >
    > > > >
    > > > > 3) Device accepts any PASIDs from the guest. No
    > > > > vPASID/pPASID translation is possible. (classic vfio_pci)
    > > > > 4) Device accepts any PASID from the guest and has an
    > > > > internal vPASID/pPASID translation (enhanced vfio_pci)
    > > >
    > > > what is enhanced vfio_pci? In my writing this is for mdev
    > > > which doesn't support ENQCMD
    > >
    > > This is a vfio_pci that mediates some element of the device interface
    > > to communicate the vPASID/pPASID table to the device, using Max's
    > > series for vfio_pci drivers to inject itself into VFIO.
    > >
    > > For instance a device might send a message through the PF that the VF
    > > has a certain vPASID/pPASID translation table. This would be useful
    > > for devices that cannot use ENQCMD but still want to support migration
    > > and thus need vPASID.
    >
    > I still don't quite get. If it's a PCI device why is PASID translation required?
    > Just delegate the per-RID PASID space to user as type-3 then migrating the
    > vPASID space is just straightforward.

    This is only possible if we get rid of the global pPASID allocation
    (honestly is my preference as it makes the HW a lot simpler)

    Without vPASID the migration would need pPASID's on the RID that are
    guarenteed free.

    Jason

    \
     
     \ /
      Last update: 2021-06-04 14:09    [W:3.258 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site