linux-kernel - Re: [PATCH] iommu/vt-d: Try info->iommu in device_to

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Message-ID: <6da2adf4-6717-b562-5ee3-7e28447aa65b@linux.intel.com>
Date:   Fri, 13 May 2022 11:32:11 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Nicolin Chen <nicolinc@...dia.com>, dwmw2@...radead.org,
        joro@...tes.org, will@...nel.org
Cc:     baolu.lu@...ux.intel.com, jgg@...dia.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Try info->iommu in device_to_iommu()

On 2022/5/13 08:32, Nicolin Chen wrote:
> Local boot test and VFIO sanity test show that info->iommu can be
> used in device_to_iommu() as a fast path. So this patch adds it.
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>   drivers/iommu/intel/iommu.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 2990f80c5e08..412fca5ab9cd 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -777,6 +777,7 @@ static bool iommu_is_dummy(struct intel_iommu *iommu, struct device *dev)
>   struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
>   {
>   	struct dmar_drhd_unit *drhd = NULL;
> +	struct device_domain_info *info;
>   	struct pci_dev *pdev = NULL;
>   	struct intel_iommu *iommu;
>   	struct device *tmp;
> @@ -786,6 +787,10 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
>   	if (!dev)
>   		return NULL;
>   
> +	info = dev_iommu_priv_get(dev);
> +	if (info)
> +		return info->iommu;

device_to_iommu() also returns device source id (@bus, @devfn).

Perhaps, we can make device_to_iommu() only for probe_device() where the
per-device info data is not initialized yet. After probe_device(), iommu
and sid are retrieved through other helpers by looking up the device
info directly?

Best regards,
baolu

> +
>   	if (dev_is_pci(dev)) {
>   		struct pci_dev *pf_pdev;
>