Messages in this thread | | | Date | Wed, 22 Jun 2022 12:39:34 +0800 | Subject | Re: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure | From | Baolu Lu <> |
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On 2022/6/22 11:31, Tian, Kevin wrote: >> From: Baolu Lu <baolu.lu@linux.intel.com> >> Sent: Wednesday, June 22, 2022 11:28 AM >> >> On 2022/6/22 11:06, Tian, Kevin wrote: >>>> From: Baolu Lu<baolu.lu@linux.intel.com> >>>> Sent: Tuesday, June 21, 2022 5:04 PM >>>> >>>> On 2022/6/21 13:48, Tian, Kevin wrote: >>>>>> From: Baolu Lu<baolu.lu@linux.intel.com> >>>>>> Sent: Tuesday, June 21, 2022 12:28 PM >>>>>> >>>>>> On 2022/6/21 11:46, Tian, Kevin wrote: >>>>>>>> From: Baolu Lu<baolu.lu@linux.intel.com> >>>>>>>> Sent: Tuesday, June 21, 2022 11:39 AM >>>>>>>> >>>>>>>> On 2022/6/21 10:54, Tian, Kevin wrote: >>>>>>>>>> From: Lu Baolu<baolu.lu@linux.intel.com> >>>>>>>>>> Sent: Monday, June 20, 2022 4:17 PM >>>>>>>>>> @@ -2564,7 +2564,7 @@ static int domain_add_dev_info(struct >>>>>>>>>> dmar_domain *domain, struct device *dev) >>>>>>>>>> ret = intel_pasid_setup_second_level(iommu, >>>>>>>>>> domain, >>>>>>>>>> dev, PASID_RID2PASID); >>>>>>>>>> spin_unlock_irqrestore(&iommu->lock, flags); >>>>>>>>>> - if (ret) { >>>>>>>>>> + if (ret && ret != -EBUSY) { >>>>>>>>>> dev_err(dev, "Setup RID2PASID failed\n"); >>>>>>>>>> dmar_remove_one_dev_info(dev); >>>>>>>>>> return ret; >>>>>>>>>> -- >>>>>>>>>> 2.25.1 >>>>>>>>> It's cleaner to avoid this error at the first place, i.e. only do the >>>>>>>>> setup when the first device is attached to the pasid table. >>>>>>>> The logic that identifies the first device might introduce additional >>>>>>>> unnecessary complexity. Devices that share a pasid table are rare. I >>>>>>>> even prefer to give up sharing tables so that the code can be >>>>>>>> simpler.:-) >>>>>>>> >>>>>>> It's not that complex if you simply move device_attach_pasid_table() >>>>>>> out of intel_pasid_alloc_table(). Then do the setup if >>>>>>> list_empty(&pasid_table->dev) and then attach device to the >>>>>>> pasid table in domain_add_dev_info(). >>>>>> The pasid table is part of the device, hence a better place to >>>>>> allocate/free the pasid table is in the device probe/release paths. >>>>>> Things will become more complicated if we change relationship >> between >>>>>> device and it's pasid table when attaching/detaching a domain. That's >>>>>> the reason why I thought it was additional complexity. >>>>>> >>>>> If you do want to follow current route it’s still cleaner to check >>>>> whether the pasid entry has pointed to the domain in the individual >>>>> setup function instead of blindly returning -EBUSY and then ignoring >>>>> it even if a real busy condition occurs. The setup functions can >>>>> just return zero for this benign alias case. >>>> Kevin, how do you like this one? >>>> >>>> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c >>>> index cb4c1d0cf25c..ecffd0129b2b 100644 >>>> --- a/drivers/iommu/intel/pasid.c >>>> +++ b/drivers/iommu/intel/pasid.c >>>> @@ -575,6 +575,16 @@ static inline int pasid_enable_wpe(struct >>>> pasid_entry *pte) >>>> return 0; >>>> }; >>>> >>>> +/* >>>> + * Return true if @pasid is RID2PASID and the domain @did has already >>>> + * been setup to the @pte. Otherwise, return false. >>>> + */ >>>> +static inline bool >>>> +rid2pasid_domain_valid(struct pasid_entry *pte, u32 pasid, u16 did) >>>> +{ >>>> + return pasid == PASID_RID2PASID && pasid_get_domain_id(pte) == >>>> did; >>>> +} >>> better this is not restricted to RID2PASID only, e.g. >> pasid_pte_match_domain() >>> and then read pasid from the pte to compare with the pasid argument. >>> >> >> The pasid value is not encoded in the pasid table entry. This validity >> check is only for RID2PASID as alias devices share the single RID2PASID >> entry. For other cases, we should always return -EBUSY as what the code >> is doing now. >> > > You are right.
Very appreciated for your input. I will update it with a v2.
Best regards, baolu
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