From: Jason Gunthorpe via iommu <iommu@lists.linux-foundation.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kvm@vger.kernel.org, rafael@kernel.org,
David Airlie <airlied@linux.ie>,
linux-pci@vger.kernel.org,
Thierry Reding <thierry.reding@gmail.com>,
Diana Craciun <diana.craciun@oss.nxp.com>,
Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>,
Ashok Raj <ashok.raj@intel.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Christoph Hellwig <hch@infradead.org>,
Stuart Yoder <stuyoder@gmail.com>,
Kevin Tian <kevin.tian@intel.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Alex Williamson <alex.williamson@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Dan Williams <dan.j.williams@intel.com>,
Cornelia Huck <cohuck@redhat.com>,
linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>,
iommu@lists.linux-foundation.org,
Jacob jun Pan <jacob.jun.pan@intel.com>,
Daniel Vetter <daniel@ffwll.ch>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v6 02/11] driver core: Add dma_cleanup callback in bus_type
Date: Wed, 23 Feb 2022 10:09:01 -0400 [thread overview]
Message-ID: <20220223140901.GP10061@nvidia.com> (raw)
In-Reply-To: <YhY/a9wTjmYXsuwt@kroah.com>
On Wed, Feb 23, 2022 at 03:06:35PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Feb 23, 2022 at 09:46:27AM -0400, Jason Gunthorpe wrote:
> > On Wed, Feb 23, 2022 at 01:04:00PM +0000, Robin Murphy wrote:
> >
> > > 1 - tmp->driver is non-NULL because tmp is already bound.
> > > 1.a - If tmp->driver->driver_managed_dma == 0, the group must currently be
> > > DMA-API-owned as a whole. Regardless of what driver dev has unbound from,
> > > its removal does not release someone else's DMA API (co-)ownership.
> >
> > This is an uncommon locking pattern, but it does work. It relies on
> > the mutex being an effective synchronization barrier for an unlocked
> > store:
> >
> > WRITE_ONCE(dev->driver, NULL)
>
> Only the driver core should be messing with the dev->driver pointer as
> when it does so, it already has the proper locks held. Do I need to
> move that to a "private" location so that nothing outside of the driver
> core can mess with it?
It would be nice, I've seen a abuse and mislocking of it in drivers
Jason
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WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
Christoph Hellwig <hch@infradead.org>,
Joerg Roedel <joro@8bytes.org>,
Alex Williamson <alex.williamson@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Kevin Tian <kevin.tian@intel.com>,
Ashok Raj <ashok.raj@intel.com>,
kvm@vger.kernel.org, rafael@kernel.org,
David Airlie <airlied@linux.ie>,
linux-pci@vger.kernel.org,
Thierry Reding <thierry.reding@gmail.com>,
Diana Craciun <diana.craciun@oss.nxp.com>,
Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>,
Stuart Yoder <stuyoder@gmail.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Cornelia Huck <cohuck@redhat.com>,
linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>,
iommu@lists.linux-foundation.org,
Jacob jun Pan <jacob.jun.pan@intel.com>,
Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH v6 02/11] driver core: Add dma_cleanup callback in bus_type
Date: Wed, 23 Feb 2022 10:09:01 -0400 [thread overview]
Message-ID: <20220223140901.GP10061@nvidia.com> (raw)
In-Reply-To: <YhY/a9wTjmYXsuwt@kroah.com>
On Wed, Feb 23, 2022 at 03:06:35PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Feb 23, 2022 at 09:46:27AM -0400, Jason Gunthorpe wrote:
> > On Wed, Feb 23, 2022 at 01:04:00PM +0000, Robin Murphy wrote:
> >
> > > 1 - tmp->driver is non-NULL because tmp is already bound.
> > > 1.a - If tmp->driver->driver_managed_dma == 0, the group must currently be
> > > DMA-API-owned as a whole. Regardless of what driver dev has unbound from,
> > > its removal does not release someone else's DMA API (co-)ownership.
> >
> > This is an uncommon locking pattern, but it does work. It relies on
> > the mutex being an effective synchronization barrier for an unlocked
> > store:
> >
> > WRITE_ONCE(dev->driver, NULL)
>
> Only the driver core should be messing with the dev->driver pointer as
> when it does so, it already has the proper locks held. Do I need to
> move that to a "private" location so that nothing outside of the driver
> core can mess with it?
It would be nice, I've seen a abuse and mislocking of it in drivers
Jason
next prev parent reply other threads:[~2022-02-23 14:09 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-18 0:55 [PATCH v6 00/11] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 01/11] iommu: Add dma ownership management interfaces Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-19 7:31 ` Christoph Hellwig
2022-02-19 7:31 ` Christoph Hellwig
2022-02-21 4:02 ` Lu Baolu
2022-02-21 4:02 ` Lu Baolu
2022-02-23 18:00 ` Robin Murphy
2022-02-23 18:00 ` Robin Murphy
2022-02-23 18:02 ` Jason Gunthorpe via iommu
2022-02-23 18:02 ` Jason Gunthorpe
2022-02-23 18:20 ` Robin Murphy
2022-02-23 18:20 ` Robin Murphy
2022-02-23 18:32 ` Jason Gunthorpe via iommu
2022-02-23 18:32 ` Jason Gunthorpe
2022-02-24 5:16 ` Lu Baolu
2022-02-24 5:16 ` Lu Baolu
2022-02-24 5:29 ` Lu Baolu
2022-02-24 5:29 ` Lu Baolu
2022-02-24 8:58 ` Robin Murphy
2022-02-24 8:58 ` Robin Murphy
2022-02-24 5:21 ` Lu Baolu
2022-02-24 5:21 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 02/11] driver core: Add dma_cleanup callback in bus_type Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-19 7:32 ` Christoph Hellwig
2022-02-19 7:32 ` Christoph Hellwig
2022-02-21 20:43 ` Robin Murphy
2022-02-21 20:43 ` Robin Murphy
2022-02-21 23:48 ` Jason Gunthorpe via iommu
2022-02-21 23:48 ` Jason Gunthorpe
2022-02-22 4:48 ` Lu Baolu
2022-02-22 4:48 ` Lu Baolu
2022-02-22 10:58 ` Robin Murphy
2022-02-22 10:58 ` Robin Murphy
2022-02-22 15:16 ` Jason Gunthorpe via iommu
2022-02-22 15:16 ` Jason Gunthorpe
2022-02-22 21:18 ` Robin Murphy
2022-02-22 21:18 ` Robin Murphy
2022-02-22 23:53 ` Jason Gunthorpe via iommu
2022-02-22 23:53 ` Jason Gunthorpe
2022-02-23 5:01 ` Lu Baolu
2022-02-23 5:01 ` Lu Baolu
2022-02-23 13:04 ` Robin Murphy
2022-02-23 13:04 ` Robin Murphy
2022-02-23 13:46 ` Jason Gunthorpe via iommu
2022-02-23 13:46 ` Jason Gunthorpe
2022-02-23 14:06 ` Greg Kroah-Hartman
2022-02-23 14:06 ` Greg Kroah-Hartman
2022-02-23 14:09 ` Jason Gunthorpe via iommu [this message]
2022-02-23 14:09 ` Jason Gunthorpe
2022-02-23 14:30 ` Jason Gunthorpe via iommu
2022-02-23 14:30 ` Jason Gunthorpe
2022-02-23 16:03 ` Greg Kroah-Hartman
2022-02-23 16:03 ` Greg Kroah-Hartman
2022-02-23 17:05 ` Robin Murphy
2022-02-23 17:05 ` Robin Murphy
2022-02-23 17:47 ` Greg Kroah-Hartman
2022-02-23 17:47 ` Greg Kroah-Hartman
2022-02-18 0:55 ` [PATCH v6 03/11] amba: Stop sharing platform_dma_configure() Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 04/11] bus: platform, amba, fsl-mc, PCI: Add device DMA ownership management Lu Baolu
2022-02-18 0:55 ` [PATCH v6 04/11] bus: platform,amba,fsl-mc,PCI: " Lu Baolu
2022-02-18 7:55 ` Greg Kroah-Hartman
2022-02-18 7:55 ` Greg Kroah-Hartman
2022-02-18 0:55 ` [PATCH v6 05/11] PCI: pci_stub: Set driver_managed_dma Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 06/11] PCI: portdrv: " Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 07/11] vfio: Set DMA ownership for VFIO devices Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 08/11] vfio: Remove use of vfio_group_viable() Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 09/11] vfio: Delete the unbound_list Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 10/11] vfio: Remove iommu group notifier Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-23 21:53 ` Alex Williamson
2022-02-23 21:53 ` Alex Williamson
2022-02-24 2:49 ` Lu Baolu
2022-02-24 2:49 ` Lu Baolu
2022-02-18 0:55 ` [PATCH v6 11/11] iommu: Remove iommu group changes notifier Lu Baolu
2022-02-18 0:55 ` Lu Baolu
2022-02-18 15:51 ` [PATCH v6 00/11] Fix BUG_ON in vfio_iommu_group_notifier() Jason Gunthorpe via iommu
2022-02-18 15:51 ` Jason Gunthorpe
2022-02-21 3:38 ` Lu Baolu
2022-02-21 3:38 ` Lu Baolu
2022-02-28 0:58 ` Lu Baolu
2022-02-28 0:58 ` Lu Baolu
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