lkml.org 
[lkml]   [2021]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 05/10] vfio: Create a vfio_device from vma lookup
On Thu, Mar 04, 2021 at 02:37:57PM -0700, Alex Williamson wrote:

> Therefore unless a bus driver opts-out by replacing vm_private_data, we
> can identify participating vmas by the vm_ops and have flags indicating
> if the vma maps device memory such that vfio_get_device_from_vma()
> should produce a device reference. The vfio IOMMU backends would also
> consume this, ie. if they get a valid vfio_device from the vma, use the
> pfn_base field directly. vfio_vm_ops would wrap the bus driver
> callbacks and provide reference counting on open/close to release this
> object.

> I'm not thrilled with a vfio_device_ops callback plumbed through
> vfio-core to do vma-to-pfn translation, so I thought this might be a
> better alternative. Thanks,

Maybe you could explain why, because I'm looking at this idea and
thinking it looks very complicated compared to a simple driver op
callback?

The implementation of such an op for vfio_pci is one line trivial, why
do we need allocated memory and a entire shim layer instead?

Shim layers are bad.

We still need a driver op of some kind because only the driver can
convert a pg_off into a PFN. Remember the big point here is to remove
the sketchy follow_pte()...

Jason

\
 
 \ /
  Last update: 2021-03-05 00:17    [W:0.060 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site