From: Yi Liu <yi.l.liu@intel.com>
To: Baolu Lu <baolu.lu@linux.intel.com>, <joro@8bytes.org>,
<jgg@nvidia.com>, <kevin.tian@intel.com>
Cc: <alex.williamson@redhat.com>, <robin.murphy@arm.com>,
<eric.auger@redhat.com>, <nicolinc@nvidia.com>,
<kvm@vger.kernel.org>, <chao.p.peng@linux.intel.com>,
<iommu@lists.linux.dev>, <zhenzhong.duan@intel.com>,
<jacob.jun.pan@intel.com>
Subject: Re: [PATCH v2 10/12] iommu/vt-d: Return if no dev_pasid is found in domain
Date: Wed, 17 Apr 2024 11:48:17 +0800 [thread overview]
Message-ID: <1619eb87-3879-42c2-a2f0-6351dd504410@intel.com> (raw)
In-Reply-To: <a0543205-18a8-4878-8b24-3d87bee24645@linux.intel.com>
On 2024/4/17 10:30, Baolu Lu wrote:
> On 4/16/24 5:21 PM, Yi Liu wrote:
>>
>> n 2024/4/15 14:04, Baolu Lu wrote:
>>> On 4/12/24 4:15 PM, Yi Liu wrote:
>>>> If no dev_pasid is found, it should be a problem of caller. So a WARN_ON
>>>> is fine, but no need to go further as nothing to be cleanup and also it
>>>> may hit unknown issue.
>>>
>>> If "... it should be a problem of caller ...", then the check and WARN()
>>> should be added in the caller instead of individual drivers.
>>>
>>>>
>>>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>>>> ---
>>>> drivers/iommu/intel/iommu.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>>> index df49aed3df5e..fff7dea012a7 100644
>>>> --- a/drivers/iommu/intel/iommu.c
>>>> +++ b/drivers/iommu/intel/iommu.c
>>>> @@ -4614,8 +4614,9 @@ static void intel_iommu_remove_dev_pasid(struct
>>>> device *dev, ioasid_t pasid,
>>>> break;
>>>> }
>>>> }
>>>> - WARN_ON_ONCE(!dev_pasid);
>>>> spin_unlock_irqrestore(&dmar_domain->lock, flags);
>>>> + if (WARN_ON_ONCE(!dev_pasid))
>>>> + return;
>>>
>>> The iommu core calls remove_dev_pasid op to tear down the translation on
>>> a pasid and park it in a BLOCKED state. Since this is a must-be-
>>> successful callback, it makes no sense to return before tearing down the
>>> pasid table entry.
>>
>> but if no dev_pasid is found, does it mean there is no pasid table entry
>> to be destroyed? That's why I think it deserves a warn, but no need to
>> continue.
>
> The pasid table is allocated in the iommu probe path, hence the entry is
> *always* there. Teardown a pasid translation just means zeroing out all
> fields of the entry.
aha, I didn't make it clear. It should be no present pasid entry if no
dev_pasid. Anyhow, I noticed intel_pasid_tear_down_entry() checks present
first before going ahead. So keep going is ok to me now.
>>
>>>
>>> From the Intel iommu driver's perspective, the pasid devices have
>>> already been tracked in the core, hence the dev_pasid is a duplicate and
>>> will be removed later, so don't use it for other purposes.
>>
>>
>> good to know it. But for the current code, if we continue, it would hit
>> call trace in the end in the intel_iommu_debugfs_remove_dev_pasid().
>
> The debugfs interface should be designed to be self-contained. That
> means, even if one passes a NULL pointer to
> intel_iommu_debugfs_remove_dev_pasid(), it should handle it gracefully.
TBH. I don't know if it is necessary to make every internal helpers
self-contained. It looks to be more readable to avoid unnecessary
function calls in the caller side. :)
--
Regards,
Yi Liu
next prev parent reply other threads:[~2024-04-17 3:44 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 8:15 [PATCH v2 00/12] iommufd support pasid attach/replace Yi Liu
2024-04-12 8:15 ` [PATCH v2 01/12] iommu: Pass old domain to set_dev_pasid op Yi Liu
2024-04-15 5:32 ` Baolu Lu
2024-04-15 11:54 ` Jason Gunthorpe
2024-04-16 2:07 ` Baolu Lu
2024-04-16 17:47 ` Jason Gunthorpe
2024-04-12 8:15 ` [PATCH v2 02/12] iommu: Introduce a replace API for device pasid Yi Liu
2024-04-16 3:01 ` Duan, Zhenzhong
2024-04-16 9:18 ` Yi Liu
2024-04-17 8:44 ` Tian, Kevin
2024-04-17 12:17 ` Jason Gunthorpe
2024-04-18 0:08 ` Tian, Kevin
2024-04-29 13:55 ` Jason Gunthorpe
2024-04-30 5:00 ` Yi Liu
2024-04-30 12:26 ` Jason Gunthorpe
2024-04-12 8:15 ` [PATCH v2 03/12] iommufd: replace attach_fn with a structure Yi Liu
2024-04-12 8:15 ` [PATCH v2 04/12] iommufd: Support attach/replace hwpt per pasid Yi Liu
2024-04-29 13:56 ` Jason Gunthorpe
2024-04-12 8:15 ` [PATCH v2 05/12] iommu: Allow iommu driver to populate the max_pasids Yi Liu
2024-04-15 5:41 ` Baolu Lu
2024-04-17 8:49 ` Tian, Kevin
2024-04-20 5:45 ` Yi Liu
2024-04-22 11:52 ` Jason Gunthorpe
2024-04-12 8:15 ` [PATCH v2 06/12] iommufd/selftest: Add set_dev_pasid and remove_dev_pasid in mock iommu Yi Liu
2024-04-12 8:15 ` [PATCH v2 07/12] iommufd/selftest: Add a helper to get test device Yi Liu
2024-04-12 8:15 ` [PATCH v2 08/12] iommufd/selftest: Add test ops to test pasid attach/detach Yi Liu
2024-04-12 8:15 ` [PATCH v2 09/12] iommufd/selftest: Add coverage for iommufd " Yi Liu
2024-04-12 8:15 ` [PATCH v2 10/12] iommu/vt-d: Return if no dev_pasid is found in domain Yi Liu
2024-04-15 6:04 ` Baolu Lu
2024-04-16 9:21 ` Yi Liu
2024-04-17 2:30 ` Baolu Lu
2024-04-17 3:48 ` Yi Liu [this message]
2024-04-17 9:03 ` Tian, Kevin
2024-04-17 9:36 ` Yi Liu
2024-04-12 8:15 ` [PATCH v2 11/12] iommu/vt-d: Make intel_iommu_set_dev_pasid() to handle domain replacement Yi Liu
2024-04-17 9:19 ` Tian, Kevin
2024-04-17 9:35 ` Yi Liu
2024-04-17 12:19 ` Jason Gunthorpe
2024-04-12 8:15 ` [PATCH v2 12/12] iommu/vt-d: Add set_dev_pasid callback for nested domain Yi Liu
2024-04-17 9:25 ` Tian, Kevin
2024-04-30 9:19 ` Yi Liu
2024-05-06 7:42 ` Baolu Lu
2024-05-06 13:36 ` Jason Gunthorpe
2024-05-07 2:28 ` Yi Liu
2024-05-07 15:18 ` Jason Gunthorpe
2024-05-08 6:10 ` Yi Liu
2024-05-08 12:25 ` Jason Gunthorpe
2024-05-08 13:26 ` Yi Liu
2024-05-08 14:11 ` Jason Gunthorpe
2024-05-09 14:22 ` Liu, Yi L
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