From: Baolu Lu <baolu.lu@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
Nicolin Chen <nicolinc@nvidia.com>,
"jgg@nvidia.com" <jgg@nvidia.com>,
"Lu, Baolu" <baolu.lu@intel.com>,
"robin.murphy@arm.com" <robin.murphy@arm.com>
Cc: baolu.lu@linux.intel.com, "Liu, Yi L" <yi.l.liu@intel.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 3/3] iommufd/device: Change iommufd_hw_pagetable_has_group to device centric
Date: Wed, 1 Feb 2023 14:49:08 +0800 [thread overview]
Message-ID: <df494d34-d804-e743-023f-d1effc881628@linux.intel.com> (raw)
In-Reply-To: <BN9PR11MB52769883FEE25F0BA731220B8CD19@BN9PR11MB5276.namprd11.prod.outlook.com>
On 2023/2/1 11:07, Tian, Kevin wrote:
>> From: Nicolin Chen <nicolinc@nvidia.com>
>> Sent: Monday, January 30, 2023 6:22 PM
>>
>> On Sun, Jan 29, 2023 at 02:38:55AM -0800, Nicolin Chen wrote:
>>
>>>>> @@ -385,10 +372,8 @@ void iommufd_device_detach(struct
>>>>> iommufd_device *idev)
>>>>> struct iommufd_hw_pagetable *hwpt = idev->hwpt;
>>>>>
>>>>> mutex_lock(&hwpt->ioas->mutex);
>>>>> - mutex_lock(&hwpt->devices_lock);
>>>>> refcount_dec(hwpt->devices_users);
>>>>> - list_del(&idev->devices_item);
>>>>> - if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
>>>>> + if (iommufd_hw_pagetable_has_device(hwpt, idev->dev)) {
>>>>> if (refcount_read(hwpt->devices_users) == 1) {
>>>>> iopt_table_remove_domain(&hwpt->ioas->iopt,
>>>>> hwpt->domain);
>>>>> @@ -397,7 +382,6 @@ void iommufd_device_detach(struct
>> iommufd_device
>>>>> *idev)
>>>>> iommu_detach_group(hwpt->domain, idev->group);
>>>>> }
>>>>
>>>> emmm how do we track last device detach in a group? Here the first
>>>> device detach already leads to group detach...
>>>
>>> Oh no. That's a bug. Thanks for catching it.
>>>
>>> We need an additional refcount somewhere to track the number of
>>> attached devices in the iommu_group.
>>
>> Wondering if we can let iommu_attach/detach_device handle this:
>>
>
> that is the desired way to fully remove group awareness in iommufd.
>
> but iirc there were some concerns on changing their semantics. But
> I don't remember the detail now. Jason might know. also +Baolu/Robin.
>
> otherwise as long as the group attach/detach continues to be used
> then identifying last device in the group always needs some hack
> within iommufd itself.
I have tried to solve this problem.
https://lore.kernel.org/linux-iommu/20220106022053.2406748-1-baolu.lu@linux.intel.com/
I may need to review the original discussion to see if I can update a
new version.
Best regards,
baolu
next prev parent reply other threads:[~2023-02-01 6:49 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-28 21:18 [PATCH v2 0/3] iommufd: Remove iommufd_hw_pagetable_has_group Nicolin Chen
2023-01-28 21:18 ` [PATCH v2 1/3] iommufd: Add devices_users to track the hw_pagetable usage by device Nicolin Chen
2023-01-29 9:23 ` Tian, Kevin
2023-01-29 9:30 ` Nicolin Chen
2023-01-29 9:39 ` Tian, Kevin
2023-01-30 2:22 ` Liu, Yi L
2023-01-30 15:02 ` Jason Gunthorpe
2023-01-30 19:27 ` Nicolin Chen
2023-01-30 19:50 ` Jason Gunthorpe
2023-01-30 20:04 ` Nicolin Chen
2023-01-30 20:35 ` Jason Gunthorpe
2023-01-30 20:53 ` Nicolin Chen
2023-02-01 7:48 ` Nicolin Chen
2023-02-02 9:12 ` Nicolin Chen
2023-02-07 4:19 ` Liu, Yi L
2023-02-01 6:57 ` Nicolin Chen
2023-02-01 7:56 ` Nicolin Chen
2023-02-01 15:53 ` Jason Gunthorpe
2023-02-01 17:46 ` Nicolin Chen
2023-02-01 18:37 ` Jason Gunthorpe
2023-02-01 19:25 ` Nicolin Chen
2023-02-01 20:00 ` Jason Gunthorpe
2023-02-01 21:18 ` Nicolin Chen
2023-02-02 7:28 ` Nicolin Chen
2023-02-02 15:03 ` Jason Gunthorpe
2023-02-07 4:27 ` Liu, Yi L
2023-01-28 21:18 ` [PATCH v2 2/3] iommufd/device: Make hwpt_list list_add/del symmetric Nicolin Chen
2023-01-29 9:24 ` Tian, Kevin
2023-01-29 9:31 ` Nicolin Chen
2023-01-30 14:59 ` Jason Gunthorpe
2023-01-30 19:03 ` Nicolin Chen
2023-01-30 19:07 ` Jason Gunthorpe
2023-01-30 19:38 ` Nicolin Chen
2023-01-28 21:18 ` [PATCH v2 3/3] iommufd/device: Change iommufd_hw_pagetable_has_group to device centric Nicolin Chen
2023-01-29 9:37 ` Tian, Kevin
2023-01-29 10:38 ` Nicolin Chen
2023-01-30 0:44 ` Tian, Kevin
2023-01-30 10:22 ` Nicolin Chen
2023-02-01 3:07 ` Tian, Kevin
2023-02-01 6:49 ` Baolu Lu [this message]
2023-02-01 6:59 ` Tian, Kevin
2023-02-01 7:20 ` Nicolin Chen
2023-02-02 6:32 ` Tian, Kevin
2023-02-02 6:36 ` Nicolin Chen
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