linux-kernel - Re: [PATCH 3/9] iommu: Add common code to handle IO page faults

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Date:   Tue, 11 Jul 2023 13:50:56 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>, iommu@...ts.linux.dev,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 3/9] iommu: Add common code to handle IO page faults

Hi Lu,

On Tue, 11 Jul 2023 09:06:36 +0800, Lu Baolu <baolu.lu@...ux.intel.com>
wrote:

> The individual iommu drivers report iommu faults by calling
> iommu_report_device_fault(), where a pre-registered device fault handler
> is called to route the fault to another fault handler installed on the
> corresponding iommu domain.
> 
> The pre-registered device fault handler is static and won't be dynamic
> as the fault handler is eventually per iommu domain. Replace the device
> fault handler with a static common code to avoid unnecessary code.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/iommu.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index da340f11c5f5..41328f03e8b4 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1278,6 +1278,28 @@ int iommu_unregister_device_fault_handler(struct
> device *dev) }
>  EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
>  
> +static int iommu_handle_io_pgfault(struct device *dev,
> +				   struct iommu_fault *fault)
> +{
> +	struct iommu_domain *domain;
> +
> +	if (fault->type != IOMMU_FAULT_PAGE_REQ)
> +		return -EINVAL;
> +
> +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
> +		domain = iommu_get_domain_for_dev_pasid(dev,
> fault->prm.pasid, 0);
> +	else
> +		domain = iommu_get_domain_for_dev(dev);
we don't support IOPF w/o PASID yet, right?

> +
> +	if (!domain || !domain->iopf_handler)
> +		return -ENODEV;
> +
> +	if (domain->iopf_handler == iommu_sva_handle_iopf)
> +		return iommu_queue_iopf(fault, dev);
Just wondering why have a special treatment for SVA domain. Can
iommu_queue_iopf() be used as SVA domain->iopf_handler?

> +
> +	return domain->iopf_handler(fault, dev, domain->fault_data);
> +}
> +
>  /**
>   * iommu_report_device_fault() - Report fault event to device driver
>   * @dev: the device
> @@ -1320,7 +1342,7 @@ int iommu_report_device_fault(struct device *dev,
> struct iommu_fault_event *evt) mutex_unlock(&fparam->lock);
>  	}
>  
> -	ret = fparam->handler(&evt->fault, fparam->data);
> +	ret = iommu_handle_io_pgfault(dev, &evt->fault);
>  	if (ret && evt_pending) {
>  		mutex_lock(&fparam->lock);
>  		list_del(&evt_pending->list);


Thanks,

Jacob