RE: [PATCH 07/12] iommu/vt-d: Acquiring lock in pasid manipulation helpers

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, May 27, 2022 2:30 PM
> 
> The iommu->lock is used to protect the per-IOMMU pasid directory table
> and pasid table. Move the spinlock acquisition/release into the helpers
> to make the code self-contained.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>, with one nit

> 
> -	/* Caller must ensure PASID entry is not in use. */
> -	if (pasid_pte_is_present(pte))
> -		return -EBUSY;
> +	spin_lock(&iommu->lock);
> +	pte = get_non_present_pasid_entry(dev, pasid);
> +	if (!pte) {
> +		spin_unlock(&iommu->lock);
> +		return -ENODEV;
> +	}

I don't think above is a good abstraction and it changes the error
code for an present entry from -EBUSY to -ENODEV.