linux-kernel - RE: [PATCH v2 10/12] iommu/vt-d: Fold __dmar_remove_one_dev

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Date:   Tue, 14 Jun 2022 07:07:12 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Jason Gunthorpe" <jgg@...dia.com>
CC:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 10/12] iommu/vt-d: Fold __dmar_remove_one_dev_info()
 into its caller

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, June 14, 2022 10:52 AM
> 
> Fold __dmar_remove_one_dev_info() into dmar_remove_one_dev_info()
> which
> is its only caller. Make the spin lock critical range only cover the
> device list change code and remove some unnecessary checks.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel/iommu.c | 34 +++++++++-------------------------
>  1 file changed, 9 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index af22690f44c8..8345e0c0824c 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -295,7 +295,6 @@ static LIST_HEAD(dmar_satc_units);
>  static int g_num_of_iommus;
> 
>  static void dmar_remove_one_dev_info(struct device *dev);
> -static void __dmar_remove_one_dev_info(struct device_domain_info *info);
> 
>  int dmar_disabled = !IS_ENABLED(CONFIG_INTEL_IOMMU_DEFAULT_ON);
>  int intel_iommu_sm =
> IS_ENABLED(CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON);
> @@ -4141,20 +4140,14 @@ static void domain_context_clear(struct
> device_domain_info *info)
>  			       &domain_context_clear_one_cb, info);
>  }
> 
> -static void __dmar_remove_one_dev_info(struct device_domain_info *info)
> +static void dmar_remove_one_dev_info(struct device *dev)
>  {
> -	struct dmar_domain *domain;
> -	struct intel_iommu *iommu;
> -
> -	assert_spin_locked(&device_domain_lock);
> -
> -	if (WARN_ON(!info))
> -		return;
> -
> -	iommu = info->iommu;
> -	domain = info->domain;
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct dmar_domain *domain = info->domain;

this local variable is not required as there is just one reference
to info->domain.

btw I didn't see info->domain is cleared in this path. Is it correct?

> +	struct intel_iommu *iommu = info->iommu;
> +	unsigned long flags;
> 
> -	if (info->dev && !dev_is_real_dma_subdevice(info->dev)) {
> +	if (!dev_is_real_dma_subdevice(info->dev)) {
>  		if (dev_is_pci(info->dev) && sm_supported(iommu))
>  			intel_pasid_tear_down_entry(iommu, info->dev,
>  					PASID_RID2PASID, false);
> @@ -4164,20 +4157,11 @@ static void
> __dmar_remove_one_dev_info(struct device_domain_info *info)
>  		intel_pasid_free_table(info->dev);
>  	}
> 
> -	list_del(&info->link);
> -	domain_detach_iommu(domain, iommu);
> -}
> -
> -static void dmar_remove_one_dev_info(struct device *dev)
> -{
> -	struct device_domain_info *info;
> -	unsigned long flags;
> -
>  	spin_lock_irqsave(&device_domain_lock, flags);
> -	info = dev_iommu_priv_get(dev);
> -	if (info)
> -		__dmar_remove_one_dev_info(info);
> +	list_del(&info->link);
>  	spin_unlock_irqrestore(&device_domain_lock, flags);
> +
> +	domain_detach_iommu(domain, iommu);
>  }
> 
>  static int md_domain_init(struct dmar_domain *domain, int guest_width)
> --
> 2.25.1