All of lore.kernel.org
 help / color / mirror / Atom feed
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jason Gunthorpe <jgg@nvidia.com>
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 15:06:35 +0100	[thread overview]
Message-ID: <YhY/a9wTjmYXsuwt@kroah.com> (raw)
In-Reply-To: <20220223134627.GO10061@nvidia.com>

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?

thanks,

greg k-h
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jason Gunthorpe <jgg@nvidia.com>
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 15:06:35 +0100	[thread overview]
Message-ID: <YhY/a9wTjmYXsuwt@kroah.com> (raw)
In-Reply-To: <20220223134627.GO10061@nvidia.com>

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?

thanks,

greg k-h

  reply	other threads:[~2022-02-23 14:06 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 [this message]
2022-02-23 14:06                         ` Greg Kroah-Hartman
2022-02-23 14:09                         ` Jason Gunthorpe via iommu
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YhY/a9wTjmYXsuwt@kroah.com \
    --to=gregkh@linuxfoundation.org \
    --cc=airlied@linux.ie \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=bhelgaas@google.com \
    --cc=cohuck@redhat.com \
    --cc=dan.j.williams@intel.com \
    --cc=daniel@ffwll.ch \
    --cc=diana.craciun@oss.nxp.com \
    --cc=digetx@gmail.com \
    --cc=hch@infradead.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.jun.pan@intel.com \
    --cc=jgg@nvidia.com \
    --cc=jonathanh@nvidia.com \
    --cc=kch@nvidia.com \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=leoyang.li@nxp.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=rafael@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=stuyoder@gmail.com \
    --cc=thierry.reding@gmail.com \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.