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

[Bjorn Helgaas <helgaas@kernel.org>]

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.

> 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
>