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

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Message-ID: <03e70268-aadc-7ad2-276b-bf029487a5de@intel.com>
Date:   Mon, 20 Jun 2022 16:31:31 +0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Kevin Tian" <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>
CC:     Chenyi Qiang <chenyi.qiang@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH 1/1] iommu/vt-d: Fix RID2PASID setup failure

Hi Baolu,

On 2022/6/20 16:17, Lu Baolu wrote:
> 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

s/marke/marked/

> 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.

nit. this sentence is a little bit to interpret. :-) I guess what you want
to describe is the PCI alias devices should be attached to the same domain
instead of different domain. right?

also, does it apply to all domain types? e.g. the SVA domains introduced in 
"iommu: SVA and IOPF refactoring"

> Therefore the subsequent devices just try to setup the RID2PASID entry
> with the same domain, which is negligible.
> 
> Fixes: ef848b7e5a6a0 ("iommu/vt-d: Setup pasid entry for RID2PASID support")
> Reported-by: Chenyi Qiang <chenyi.qiang@...el.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Lu Baolu <baolu.lu@...ux.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;

-- 
Regards,
Yi Liu