linux-kernel - Re: [PATCH 1/3] iommu/vt-d: Remove redundant IOTLB flush

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Message-ID: <26ab1917-f087-aafa-e861-6a2478000a6f@linux.intel.com>
Date:   Fri, 20 Mar 2020 21:45:26 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     baolu.lu@...ux.intel.com, Raj Ashok <ashok.raj@...el.com>,
        Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH 1/3] iommu/vt-d: Remove redundant IOTLB flush

On 2020/3/20 12:32, Jacob Pan wrote:
> IOTLB flush already included in the PASID tear down process. There
> is no need to flush again.

It seems that intel_pasid_tear_down_entry() doesn't flush the pasid
based device TLB?

Best regards,
baolu

> 
> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>   drivers/iommu/intel-svm.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 8f42d717d8d7..1483f1845762 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -268,10 +268,9 @@ static void intel_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
>   	 * *has* to handle gracefully without affecting other processes.
>   	 */
>   	rcu_read_lock();
> -	list_for_each_entry_rcu(sdev, &svm->devs, list) {
> +	list_for_each_entry_rcu(sdev, &svm->devs, list)
>   		intel_pasid_tear_down_entry(svm->iommu, sdev->dev, svm->pasid);
> -		intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
> -	}
> +
>   	rcu_read_unlock();
>   
>   }
> @@ -731,7 +730,6 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
>   			 * large and has to be physically contiguous. So it's
>   			 * hard to be as defensive as we might like. */
>   			intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
> -			intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
>   			kfree_rcu(sdev, rcu);
>   
>   			if (list_empty(&svm->devs)) {
>