From: Yi Liu <yi.l.liu@intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"jgg@nvidia.com" <jgg@nvidia.com>,
"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>
Cc: "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"robin.murphy@arm.com" <robin.murphy@arm.com>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"nicolinc@nvidia.com" <nicolinc@nvidia.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"chao.p.peng@linux.intel.com" <chao.p.peng@linux.intel.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"Duan, Zhenzhong" <zhenzhong.duan@intel.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>
Subject: Re: [PATCH v2 11/12] iommu/vt-d: Make intel_iommu_set_dev_pasid() to handle domain replacement
Date: Wed, 17 Apr 2024 17:35:47 +0800 [thread overview]
Message-ID: <52e38f2f-0e45-49ab-a426-53ad57c20b0c@intel.com> (raw)
In-Reply-To: <BN9PR11MB52768C98314A95AFCD2FA6478C0F2@BN9PR11MB5276.namprd11.prod.outlook.com>
On 2024/4/17 17:19, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Friday, April 12, 2024 4:15 PM
>>
>> @@ -4646,6 +4646,10 @@ static int intel_iommu_set_dev_pasid(struct
>> iommu_domain *domain,
>> if (context_copied(iommu, info->bus, info->devfn))
>> return -EBUSY;
>>
>> + /* Block old translation */
>> + if (old)
>> + intel_iommu_remove_dev_pasid(dev, pasid, old);
>> +
>
> let's talk about one scenario.
>
> pasid#100 is currently attached to domain#1
>
> the user requests to replace pasid#100 to domain#2, which enables
> dirty tracking.
>
> this function will return error before blocking the old translation:
>
> if (domain->dirty_ops)
> return -EINVAL;
yep. From what I learned from Joao, this check was added due to no actual
usage before SIOV. If only considering vSVM, the domain attached to pasids
won't have the dirty_ops. So I was planning to remove this check when
coming to SIOV series. But let me know if it's already the time to remove
it.
>
> pasid#100 is still attached to domain#1.
>
> then the error unwinding in iommu core tries to attach pasid#100
> back to domain#1:
>
> /*
> * Rollback the devices/pasid that have attached to the new
> * domain. And it is a driver bug to fail attaching with a
> * previously good domain.
> */
> if (device == last_gdev) {
> WARN_ON(old->ops->set_dev_pasid(old, device->dev,
> pasid, NULL));
> break;
> }
>
> but intel iommu driver doesn't expect duplicated attaches e.g.
> domain_attach_iommu() will increase the refcnt of the existing
> DID but later the user will only call detach once.
good catch!!! This is a problem...Even if the domain->dirty_ops check is
removed, the set_dev_pasid() callback can fail for other reasons.
> do we want to force iommu driver to block translation upon
> any error in @set_dev_pasid (then rely on the core to recover
> it correctly) or tolerate duplicated attaches?
The second one seems better? The first option looks a too heavy especially
considering the atomic requirement in certain scenarios.
--
Regards,
Yi Liu
next prev parent reply other threads:[~2024-04-17 9:32 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
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 [this message]
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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