From: Jason Gunthorpe <jgg@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: <cohuck@redhat.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <peterx@redhat.com>
Subject: Re: [RFC PATCH 05/10] vfio: Create a vfio_device from vma lookup
Date: Thu, 4 Mar 2021 19:16:33 -0400 [thread overview]
Message-ID: <20210304231633.GP4247@nvidia.com> (raw)
In-Reply-To: <20210304143757.1ca42cfc@omen.home.shazbot.org>
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
next prev parent reply other threads:[~2021-03-04 23:16 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 16:50 [RFC PATCH 00/10] vfio: Device memory DMA mapping improvements Alex Williamson
2021-02-22 16:50 ` [RFC PATCH 01/10] vfio: Create vfio_fs_type with inode per device Alex Williamson
2021-02-26 5:38 ` Christoph Hellwig
2021-02-26 13:15 ` Jason Gunthorpe
2021-02-22 16:50 ` [RFC PATCH 02/10] vfio: Update vfio_add_group_dev() API Alex Williamson
2021-02-22 17:01 ` Jason Gunthorpe
2021-02-22 16:50 ` [RFC PATCH 03/10] vfio: Export unmap_mapping_range() wrapper Alex Williamson
2021-02-22 16:51 ` [RFC PATCH 04/10] vfio/pci: Use vfio_device_unmap_mapping_range() Alex Williamson
2021-02-22 17:22 ` Jason Gunthorpe
2021-02-24 21:55 ` Alex Williamson
2021-02-25 0:57 ` Jason Gunthorpe
2021-02-22 16:51 ` [RFC PATCH 05/10] vfio: Create a vfio_device from vma lookup Alex Williamson
2021-02-22 17:29 ` Jason Gunthorpe
2021-02-24 21:55 ` Alex Williamson
2021-02-25 0:06 ` Jason Gunthorpe
2021-02-25 22:21 ` Alex Williamson
2021-02-25 23:49 ` Jason Gunthorpe
2021-03-04 21:37 ` Alex Williamson
2021-03-04 23:16 ` Jason Gunthorpe [this message]
2021-03-05 0:07 ` Alex Williamson
2021-03-05 0:36 ` Jason Gunthorpe
2021-02-22 16:51 ` [RFC PATCH 06/10] vfio: Add a device notifier interface Alex Williamson
2021-02-22 16:51 ` [RFC PATCH 07/10] vfio/pci: Notify on device release Alex Williamson
2021-02-22 16:52 ` [RFC PATCH 08/10] vfio/type1: Refactor pfn_list clearing Alex Williamson
2021-02-22 16:52 ` [RFC PATCH 09/10] vfio/type1: Pass iommu and dma objects through to vaddr_get_pfn Alex Williamson
2021-02-22 16:52 ` [RFC PATCH 10/10] vfio/type1: Register device notifier Alex Williamson
2021-02-22 17:55 ` Jason Gunthorpe
2021-02-24 21:55 ` Alex Williamson
2021-02-25 0:22 ` Jason Gunthorpe
2021-02-25 17:54 ` Peter Xu
2021-02-25 18:19 ` Jason Gunthorpe
2021-02-25 19:06 ` Peter Xu
2021-02-25 19:17 ` Jason Gunthorpe
2021-02-25 19:54 ` Peter Xu
2021-02-26 5:47 ` Christoph Hellwig
2021-02-22 18:00 ` [RFC PATCH 00/10] vfio: Device memory DMA mapping improvements Jason Gunthorpe
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