Re: [PATCH] iommu/vt-d: improve ITE fault handling if device was released

[Ethan Zhao <haifeng.zhao@linux.intel.com>]

On 3/1/2024 5:07 AM, Bjorn Helgaas wrote:
> On Wed, Feb 28, 2024 at 11:07:24PM -0500, Ethan Zhao wrote:
>> Break the loop to blindly retry the timeout ATS invalidation request
>> after ITE fault hit if device was released or isn't present anymore.
>>
>> This is part of the followup of prior proposed patchset
>>
>> https://do-db2.lkml.org/lkml/2024/2/22/350
> Use lore URL, please.

Sure !

>
>> Fixes: 6ba6c3a4cacf ("VT-d: add device IOTLB invalidation support")
>> Signed-off-by: Ethan Zhao <haifeng.zhao@linux.intel.com>
>> ---
>>   drivers/iommu/intel/dmar.c | 25 +++++++++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
>> index d14797aabb7a..d01d68205557 100644
>> --- a/drivers/iommu/intel/dmar.c
>> +++ b/drivers/iommu/intel/dmar.c
>> @@ -1273,6 +1273,9 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
>>   {
>>   	u32 fault;
>>   	int head, tail;
>> +	u64 iqe_err, ite_sid;
>> +	struct device *dev = NULL;
>> +	struct pci_dev *pdev = NULL;
>>   	struct q_inval *qi = iommu->qi;
>>   	int shift = qi_shift(iommu);
>>   
>> @@ -1317,6 +1320,13 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
>>   		tail = readl(iommu->reg + DMAR_IQT_REG);
>>   		tail = ((tail >> shift) - 1 + QI_LENGTH) % QI_LENGTH;
>>   
>> +		/*
>> +		 * SID field is valid only when the ITE field is Set in FSTS_REG
>> +		 * see Intel VT-d spec r4.1, section 11.4.9.9
>> +		 */
>> +		iqe_err = dmar_readq(iommu->reg + DMAR_IQER_REG);
>> +		ite_sid = DMAR_IQER_REG_ITESID(iqe_err);
>> +
>>   		writel(DMA_FSTS_ITE, iommu->reg + DMAR_FSTS_REG);
>>   		pr_info("Invalidation Time-out Error (ITE) cleared\n");
>>   
>> @@ -1326,6 +1336,21 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
>>   			head = (head - 2 + QI_LENGTH) % QI_LENGTH;
>>   		} while (head != tail);
>>   
>> +		/*
>> +		 * If got ITE, we need to check if the sid of ITE is one of the
>> +		 * current valid ATS invalidation target devices, if no, or the
>> +		 * target device isn't presnet, don't try this request anymore.
>> +		 * 0 value of ite_sid means old VT-d device, no ite_sid value.
>> +		 */
>> +		if (ite_sid) {
>> +			dev = device_rbtree_find(iommu, ite_sid);
>> +			if (!dev || !dev_is_pci(dev))
>> +				return -ETIMEDOUT;
>> +			pdev = to_pci_dev(dev);
>> +			if (!pci_device_is_present(pdev) &&
>> +				ite_sid == pci_dev_id(pci_physfn(pdev)))
>> +				return -ETIMEDOUT;
>> +		}
>>   		if (qi->desc_status[wait_index] == QI_ABORT)
>>   			return -EAGAIN;
>>   	}
>> -- 
>> 2.31.1
>>