linux-kernel - Re: [PATCH 1/2] iommu/vt-d: Convert dmar_ats

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Date: Mon, 24 Jun 2024 16:12:04 +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>, Jacob Pan
	<jacob.jun.pan@...ux.intel.com>
CC: Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] iommu/vt-d: Convert dmar_ats_supported() to return
 bool

On 2024/6/24 13:25, Lu Baolu wrote:
> dmar_ats_supported() returns an integer that is used as a boolean. Since
> it all it needs is to return true or false, change the return type from

nit: a redundant "it" is used here.

> int to bool to make it a bit more readable and obvious.
> 
> Cleanup this helper accordingly with no functional change intended.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 33 ++++++++++++++++++---------------
>   1 file changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 38cda454fc64..07e394dfccc1 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -3043,15 +3043,15 @@ static struct dmar_satc_unit *dmar_find_matched_satc_unit(struct pci_dev *dev)
>   	return satcu;
>   }
>   
> -static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
> +static bool dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   {
> -	int i, ret = 1;
> -	struct pci_bus *bus;
>   	struct pci_dev *bridge = NULL;
> -	struct device *tmp;
> -	struct acpi_dmar_atsr *atsr;
>   	struct dmar_atsr_unit *atsru;
>   	struct dmar_satc_unit *satcu;
> +	struct acpi_dmar_atsr *atsr;
> +	struct pci_bus *bus;
> +	struct device *tmp;
> +	int i;
>   
>   	dev = pci_physfn(dev);
>   	satcu = dmar_find_matched_satc_unit(dev);
> @@ -3069,11 +3069,11 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   		bridge = bus->self;
>   		/* If it's an integrated device, allow ATS */
>   		if (!bridge)
> -			return 1;
> +			return true;
>   		/* Connected via non-PCIe: no ATS */
>   		if (!pci_is_pcie(bridge) ||
>   		    pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE)
> -			return 0;
> +			return false;
>   		/* If we found the root port, look it up in the ATSR */
>   		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
>   			break;
> @@ -3085,18 +3085,21 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   		if (atsr->segment != pci_domain_nr(dev->bus))
>   			continue;
>   
> -		for_each_dev_scope(atsru->devices, atsru->devices_cnt, i, tmp)
> -			if (tmp == &bridge->dev)
> -				goto out;
> +		for_each_dev_scope(atsru->devices, atsru->devices_cnt, i, tmp) {
> +			if (tmp == &bridge->dev) {
> +				rcu_read_unlock();
> +				return true;
> +			}
> +		}
>   
> -		if (atsru->include_all)
> -			goto out;
> +		if (atsru->include_all) {
> +			rcu_read_unlock();
> +			return true;

It appears to me that two gotos is better than opening code. :) Anyhow.

Reviewed-by: Yi Liu <yi.l.liu@...el.com>


> +		}
>   	}
> -	ret = 0;
> -out:
>   	rcu_read_unlock();
>   
> -	return ret;
> +	return false;
>   }
>   
>   int dmar_iommu_notify_scope_dev(struct dmar_pci_notify_info *info)

-- 
Regards,
Yi Liu