Re: [Intel-gfx] [PATCH v4 00/14] Provide core infrastructure for managing open/release

From: Alex Williamson <alex.williamson@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: David Airlie <airlied@linux.ie>,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>, Daniel Vetter <daniel@ffwll.ch>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	dri-devel@lists.freedesktop.org,
	Eric Auger <eric.auger@redhat.com>,
	Eric Farman <farman@linux.ibm.com>,
	Harald Freudenberger <freude@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	intel-gfx@lists.freedesktop.org,
	intel-gvt-dev@lists.freedesktop.org,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Jason Herne <jjherne@linux.ibm.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	kvm@vger.kernel.org, Kirti Wankhede <kwankhede@nvidia.com>,
	linux-doc@vger.kernel.org, linux-s390@vger.kernel.org,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Halil Pasic <pasic@linux.ibm.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Vineeth Vijayan <vneethv@linux.ibm.com>,
	Zhi Wang <zhi.a.wang@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	Christoph Hellwig <hch@lst.de>,
	Leon Romanovsky <leonro@nvidia.com>,
	Max Gurtovoy <mgurtovoy@nvidia.com>,
	Yishai Hadas <yishaih@nvidia.com>,
	Zhenyu Wang <zhenyuw@linux.intel.com>
Subject: Re: [Intel-gfx] [PATCH v4 00/14] Provide core infrastructure for managing open/release
Date: Wed, 11 Aug 2021 16:08:30 -0600	[thread overview]
Message-ID: <20210811160830.0c17b085.alex.williamson@redhat.com> (raw)
In-Reply-To: <0-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com>

On Thu,  5 Aug 2021 22:18:56 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:

> This is in support of Max's series to split vfio-pci. For that to work the
> reflck concept embedded in vfio-pci needs to be sharable across all of the
> new VFIO PCI drivers which motivated re-examining how this is
> implemented.
> 
> Another significant issue is how the VFIO PCI core includes code like:
> 
>    if (pci_dev_driver(pdev) != &vfio_pci_driver)
> 
> Which is not scalable if there are going to be multiple different driver
> types.
> 
> This series takes the approach of moving the "reflck" mechanism into the
> core code as a "device set". Each vfio_device driver can specify how
> vfio_devices are grouped into the set using a key and the set comes along
> with a set-global mutex. The core code manages creating per-device set
> memory and associating it with each vfio_device.
> 
> In turn this allows the core code to provide an open/close_device()
> operation that is called only for the first/last FD, and is called under
> the global device set lock.
> 
> Review of all the drivers show that they are either already open coding
> the first/last semantic or are buggy and missing it. All drivers are
> migrated/fixed to the new open/close_device ops and the unused per-FD
> open()/release() ops are deleted.
> 
> The special behavior of PCI around the bus/slot "reset group" is recast in
> terms of the device set which conslidates the reflck, eliminates two
> touches of pci_dev_driver(), and allows the reset mechanism to share
> across all VFIO PCI drivers. PCI is changed to acquire devices directly
> from the device set instead of trying to work backwards from the struct
> pci_device.
> 
> Overall a few minor bugs are squashed and quite a bit of code is removed
> through consolidation.
> 
> v4:
>  - Fix use-after-free typo in mbochs error unwind
>  - Allow mdevs to work when they don't have open/release ops, for
>    bisect-ability
>  - Redo the vfio_pci_try_bus_reset() patch, make it dev_set centric
>  - Change VFIO_DEVICE_PCI_HOT_RESET to align with the new
>    vfio_pci_try_bus_reset() design

Applied to vfio next branch for v5.15 with Connie and Christoph's
additional Reviewed-bys.  Thanks,

Alex