From: Jason Gunthorpe <jgg@nvidia.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: "iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
Lu Baolu <baolu.lu@linux.intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Nicolin Chen <nicolinc@nvidia.com>,
"Liu, Yi L" <yi.l.liu@intel.com>
Subject: Re: [PATCH v3 12/17] iommufd: Add iommufd_device_replace()
Date: Fri, 24 Mar 2023 12:03:39 -0300 [thread overview]
Message-ID: <ZB27y2WsrYr9KLFr@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB5276B41014B2A28952B626B58C849@BN9PR11MB5276.namprd11.prod.outlook.com>
On Fri, Mar 24, 2023 at 01:42:58AM +0000, Tian, Kevin wrote:
> > > > + /* Move the refcounts held by the device_list to the new hwpt */
> > > > + refcount_add(num_devices, &hwpt->obj.users);
> > > > + if (num_devices > 1)
> > > > + WARN_ON(refcount_sub_and_test(num_devices - 1,
> > > > + &old_hwpt->obj.users));
> > >
> > > A comment is welcomed to match "caller must destroy old_hwpt".
> >
> > ??
> >
>
> It's not intuitive when moving the refcnt why we subtract num_devices
> from the old_hwpt only when it's greater than 1. It's really about
> the destroy must be done by the caller.
/*
* Move the refcounts held by the device_list to the new hwpt. Retain a
* refcount for this thread as the caller will free it.
*/
Jason
next prev parent reply other threads:[~2023-03-24 15:03 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 19:14 [PATCH v3 00/17] Add iommufd physical device operations for replace and alloc hwpt Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 01/17] iommufd: Move isolated msi enforcement to iommufd_device_bind() Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 02/17] iommufd: Add iommufd_group Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 03/17] iommufd: Replace the hwpt->devices list with iommufd_group Jason Gunthorpe
2023-03-23 7:21 ` Tian, Kevin
2023-03-23 14:23 ` Jason Gunthorpe
2023-03-24 1:37 ` Tian, Kevin
2023-03-24 15:02 ` Jason Gunthorpe
2023-03-28 2:32 ` Tian, Kevin
2023-03-28 11:38 ` Jason Gunthorpe
2023-03-29 3:03 ` Tian, Kevin
2023-04-11 14:31 ` Jason Gunthorpe
2023-04-12 8:27 ` Tian, Kevin
2023-04-12 11:17 ` Jason Gunthorpe
2023-04-13 2:52 ` Tian, Kevin
2023-04-14 13:31 ` Jason Gunthorpe
2023-04-20 6:15 ` Tian, Kevin
2023-04-20 15:34 ` Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 04/17] iommu: Export iommu_get_resv_regions() Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 05/17] iommufd: Keep track of each device's reserved regions instead of groups Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 06/17] iommufd: Use the iommufd_group to avoid duplicate MSI setup Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 07/17] iommufd: Make sw_msi_start a group global Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 08/17] iommufd: Move putting a hwpt to a helper function Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 09/17] iommufd: Add enforced_cache_coherency to iommufd_hw_pagetable_alloc() Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 10/17] iommufd: Reorganize iommufd_device_attach into iommufd_device_change_pt Jason Gunthorpe
2023-03-23 7:25 ` Tian, Kevin
2023-03-23 14:26 ` Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 11/17] iommu: Introduce a new iommu_group_replace_domain() API Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 12/17] iommufd: Add iommufd_device_replace() Jason Gunthorpe
2023-03-23 7:31 ` Tian, Kevin
2023-03-23 14:30 ` Jason Gunthorpe
2023-03-24 1:42 ` Tian, Kevin
2023-03-24 15:03 ` Jason Gunthorpe [this message]
2023-03-21 19:14 ` [PATCH v3 13/17] iommufd: Make destroy_rwsem use a lock class per object type Jason Gunthorpe
2023-03-23 7:54 ` Tian, Kevin
2023-03-21 19:14 ` [PATCH v3 14/17] iommufd/selftest: Test iommufd_device_replace() Jason Gunthorpe
2023-03-23 7:57 ` Tian, Kevin
2023-03-23 14:32 ` Jason Gunthorpe
2023-03-21 19:14 ` [PATCH v3 15/17] iommufd: Add IOMMU_HWPT_ALLOC Jason Gunthorpe
2023-03-23 8:00 ` Tian, Kevin
2023-03-21 19:14 ` [PATCH v3 16/17] iommufd/selftest: Return the real idev id from selftest mock_domain Jason Gunthorpe
2023-03-23 8:02 ` Tian, Kevin
2023-03-21 19:14 ` [PATCH v3 17/17] iommufd/selftest: Add a selftest for IOMMU_HWPT_ALLOC Jason Gunthorpe
2023-03-23 8:03 ` Tian, Kevin
2023-03-23 8:04 ` [PATCH v3 00/17] Add iommufd physical device operations for replace and alloc hwpt Tian, Kevin
2023-03-23 14:35 ` Jason Gunthorpe
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