From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"will@kernel.org" <will@kernel.org>,
"robin.murphy@arm.com" <robin.murphy@arm.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"shuah@kernel.org" <shuah@kernel.org>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>
Subject: RE: [PATCH v1 2/8] iommu: Introduce a new iommu_group_replace_domain() API
Date: Tue, 7 Feb 2023 00:32:50 +0000 [thread overview]
Message-ID: <BN9PR11MB52769E24B07CA7296D8BEAF28CDB9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <Y+D/vWwRLD27slQz@nvidia.com>
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Monday, February 6, 2023 9:25 PM
>
> On Mon, Feb 06, 2023 at 06:57:35AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@nvidia.com>
> > > Sent: Friday, February 3, 2023 11:03 PM
> > >
> > > On Fri, Feb 03, 2023 at 08:26:44AM +0000, Tian, Kevin wrote:
> > > > > From: Nicolin Chen <nicolinc@nvidia.com>
> > > > > Sent: Thursday, February 2, 2023 3:05 PM
> > > > >
> > > > > All drivers are already required to support changing between active
> > > > > UNMANAGED domains when using their attach_dev ops.
> > > >
> > > > All drivers which don't have *broken* UNMANAGED domain?
> > >
> > > No, all drivers.. It has always been used by VFIO.
> >
> > existing iommu_attach_group() doesn't support changing between
> > two UNMANAGED domains. only from default->unmanaged or
> > blocking->unmanaged.
>
> Yes, but before we added the blocking domains VFIO was changing
> between unmanaged domains. Blocking domains are so new that no driver
> could have suddenly started to depend on this.
In legacy VFIO unmanaged domain was 1:1 associated with vfio
container. I didn't say how a group can switch between two
containers w/o going through transition to/from the default
domain, i.e. detach from 1st container and then attach to the 2nd.
> > btw looking at the code __iommu_group_set_domain():
> >
> > * Note that this is called in error unwind paths, attaching to a
> > * domain that has already been attached cannot fail.
> > */
> > ret = __iommu_group_for_each_dev(group, new_domain,
> > iommu_group_do_attach_device);
> >
> > with that we don't need fall back to core domain in above error
> > unwinding per this comment.
>
> That does make some sense.
>
> I tried to make a patch to consolidate all this error handling once,
> that would be the better way to approach this.
that would be good.
>
> > > In this case the API cannot retain a hidden reference to the new
> > > domain, so it must be purged, one way or another.
> >
> > Could you elaborate where the hidden reference is retained?
>
> Inside the driver, it can keep track of the domain pointer if
> attach_dev succeeds
>
Are you referring to no error unwinding in __iommu_group_for_each_dev()
so if it is failed some devices may have attach_dev succeeds then simply
recovering group->domain in __iommu_attach_group() is insufficient?
next prev parent reply other threads:[~2023-02-07 0:33 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-02 7:05 [PATCH v1 0/8] Add IO page table replacement support Nicolin Chen
2023-02-02 7:05 ` [PATCH v1 1/8] iommu: Move dev_iommu_ops() to private header Nicolin Chen
2023-02-02 7:05 ` [PATCH v1 2/8] iommu: Introduce a new iommu_group_replace_domain() API Nicolin Chen
2023-02-02 10:21 ` Baolu Lu
2023-02-02 19:14 ` Nicolin Chen
2023-02-03 1:33 ` Baolu Lu
2023-02-03 1:41 ` Nicolin Chen
2023-02-03 2:35 ` Baolu Lu
2023-02-03 8:26 ` Tian, Kevin
2023-02-03 15:03 ` Jason Gunthorpe
2023-02-03 17:53 ` Nicolin Chen
2023-02-06 6:57 ` Tian, Kevin
2023-02-06 13:25 ` Jason Gunthorpe
2023-02-07 0:32 ` Tian, Kevin [this message]
2023-02-07 12:22 ` Jason Gunthorpe
2023-02-08 4:25 ` Tian, Kevin
2023-02-08 12:42 ` Jason Gunthorpe
2023-02-07 19:16 ` Nicolin Chen
2023-02-03 17:45 ` Nicolin Chen
2023-02-06 6:40 ` Tian, Kevin
2023-02-02 7:05 ` [PATCH v1 3/8] iommufd: Create access in vfio_iommufd_emulated_bind() Nicolin Chen
2023-02-03 9:23 ` Tian, Kevin
2023-02-03 9:28 ` Tian, Kevin
2023-02-02 7:05 ` [PATCH v1 4/8] iommufd/selftest: Add IOMMU_TEST_OP_ACCESS_SET_IOAS coverage Nicolin Chen
2023-02-02 7:05 ` [PATCH v1 5/8] iommufd: Add replace support in iommufd_access_set_ioas() Nicolin Chen
2023-02-03 10:10 ` Tian, Kevin
2023-02-03 12:31 ` Jason Gunthorpe
2023-02-03 22:25 ` Nicolin Chen
2023-02-02 7:05 ` [PATCH v1 6/8] iommufd/selftest: Add coverage for access->ioas replacement Nicolin Chen
2023-02-02 7:05 ` [PATCH v1 7/8] iommufd/device: Use iommu_group_replace_domain() Nicolin Chen
2023-02-06 8:46 ` Tian, Kevin
2023-02-06 19:17 ` Nicolin Chen
2023-02-07 0:37 ` Tian, Kevin
2023-02-02 7:05 ` [PATCH v1 8/8] vfio-iommufd: Support IO page table replacement Nicolin Chen
2023-02-06 8:49 ` Tian, Kevin
2023-02-06 18:54 ` Nicolin Chen
2023-02-03 8:09 ` [PATCH v1 0/8] Add IO page table replacement support Tian, Kevin
2023-02-03 15:04 ` Jason Gunthorpe
2023-02-06 6:39 ` Tian, Kevin
2023-02-06 13:26 ` Jason Gunthorpe
2023-02-07 0:34 ` Tian, Kevin
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