Re: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure

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

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Hi，

在 2022/6/20 16:17, Lu Baolu 写道:
> The IOMMU driver shares the pasid table for PCI alias devices. When the
> RID2PASID entry of the shared pasid table has been filled by the first
> device, the subsequent devices will encounter the "DMAR: Setup RID2PASID
> failed" failure as the pasid entry has already been marke as present. As
> the result, the IOMMU probing process will be aborted.
>
> This fixes it by skipping RID2PASID setting if the pasid entry has been
> populated. This works because the IOMMU core ensures that only the same
> IOMMU domain can be attached to all PCI alias devices at the same time.
> Therefore the subsequent devices just try to setup the RID2PASID entry
> with the same domain, which is negligible.
     We have two customers reported the issue "DMAR: Setup RID2PASID 
failed",

Two ASPEED devices locate behind one PCIe-PCI bridge and iommu SM, PT 
mode is enabled.  Most

Interesting thing is the second device is only used by BIOS, and BIOS 
left it to OS without shutting down,

and it is useless for OS.  Is there practical case multi devices behind 
PCIe-PCI bridge share the same

PASID entry without any security concern ? these two customer's case is 
not.


Thanks,

Ethan

>
> Fixes: ef848b7e5a6a0 ("iommu/vt-d: Setup pasid entry for RID2PASID support")
> Reported-by: Chenyi Qiang<chenyi.qiang@intel.com>
> Cc:stable@vger.kernel.org
> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 44016594831d..b9966c01a2a2 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -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;

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