linux-kernel - RE: [PATCH 06/12] iommu/vt-d: Acquiring lock in domain ID allocation helpers

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Message-ID: <BN9PR11MB52760F17D3B9359EB4BB2B7B8CDF9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Wed, 1 Jun 2022 09:09:04 +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 06/12] iommu/vt-d: Acquiring lock in domain ID allocation
 helpers

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Friday, May 27, 2022 2:30 PM
> 
> The iommu->lock is used to protect the per-IOMMU domain ID resource.
> Move the spinlock acquisition/release into the helpers where domain
> IDs are allocated and freed. The device_domain_lock is irrelevant to
> domain ID resources, remove its assertion as well.

while moving the lock you also replace spin_lock_irqsave() with spin_lock().
It'd be cleaner to just do movement here and then replace all _irqsave()
in patch 8.

> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel/iommu.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 2d5f02b85de8..0da937ce0534 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1774,16 +1774,13 @@ static struct dmar_domain
> *alloc_domain(unsigned int type)
>  	return domain;
>  }
> 
> -/* Must be called with iommu->lock */
>  static int domain_attach_iommu(struct dmar_domain *domain,
>  			       struct intel_iommu *iommu)
>  {
>  	unsigned long ndomains;
> -	int num;
> -
> -	assert_spin_locked(&device_domain_lock);
> -	assert_spin_locked(&iommu->lock);
> +	int num, ret = 0;
> 
> +	spin_lock(&iommu->lock);
>  	domain->iommu_refcnt[iommu->seq_id] += 1;
>  	if (domain->iommu_refcnt[iommu->seq_id] == 1) {
>  		ndomains = cap_ndoms(iommu->cap);
> @@ -1792,7 +1789,8 @@ static int domain_attach_iommu(struct
> dmar_domain *domain,
>  		if (num >= ndomains) {
>  			pr_err("%s: No free domain ids\n", iommu->name);
>  			domain->iommu_refcnt[iommu->seq_id] -= 1;
> -			return -ENOSPC;
> +			ret = -ENOSPC;
> +			goto out_unlock;
>  		}
> 
>  		set_bit(num, iommu->domain_ids);
> @@ -1801,7 +1799,9 @@ static int domain_attach_iommu(struct
> dmar_domain *domain,
>  		domain_update_iommu_cap(domain);
>  	}
> 
> -	return 0;
> +out_unlock:
> +	spin_unlock(&iommu->lock);
> +	return ret;
>  }
> 
>  static void domain_detach_iommu(struct dmar_domain *domain,
> @@ -1809,9 +1809,7 @@ static void domain_detach_iommu(struct
> dmar_domain *domain,
>  {
>  	int num;
> 
> -	assert_spin_locked(&device_domain_lock);
> -	assert_spin_locked(&iommu->lock);
> -
> +	spin_lock(&iommu->lock);
>  	domain->iommu_refcnt[iommu->seq_id] -= 1;
>  	if (domain->iommu_refcnt[iommu->seq_id] == 0) {
>  		num = domain->iommu_did[iommu->seq_id];
> @@ -1819,6 +1817,7 @@ static void domain_detach_iommu(struct
> dmar_domain *domain,
>  		domain_update_iommu_cap(domain);
>  		domain->iommu_did[iommu->seq_id] = 0;
>  	}
> +	spin_unlock(&iommu->lock);
>  }
> 
>  static inline int guestwidth_to_adjustwidth(int gaw)
> @@ -2471,9 +2470,7 @@ static int domain_add_dev_info(struct
> dmar_domain *domain, struct device *dev)
> 
>  	spin_lock_irqsave(&device_domain_lock, flags);
>  	info->domain = domain;
> -	spin_lock(&iommu->lock);
>  	ret = domain_attach_iommu(domain, iommu);
> -	spin_unlock(&iommu->lock);
>  	if (ret) {
>  		spin_unlock_irqrestore(&device_domain_lock, flags);
>  		return ret;
> @@ -4158,7 +4155,6 @@ static void __dmar_remove_one_dev_info(struct
> device_domain_info *info)
>  {
>  	struct dmar_domain *domain;
>  	struct intel_iommu *iommu;
> -	unsigned long flags;
> 
>  	assert_spin_locked(&device_domain_lock);
> 
> @@ -4179,10 +4175,7 @@ static void __dmar_remove_one_dev_info(struct
> device_domain_info *info)
>  	}
> 
>  	list_del(&info->link);
> -
> -	spin_lock_irqsave(&iommu->lock, flags);
>  	domain_detach_iommu(domain, iommu);
> -	spin_unlock_irqrestore(&iommu->lock, flags);
>  }
> 
>  static void dmar_remove_one_dev_info(struct device *dev)
> --
> 2.25.1