linux-kernel - Re: [PATCH v9 14/14] iommu: Track iopf group instead of last fault

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Date: Tue, 9 Jan 2024 13:55:59 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 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>,
 Jacob Pan <jacob.jun.pan@...ux.intel.com>,
 Longfang Liu <liulongfang@...wei.com>, Yan Zhao <yan.y.zhao@...el.com>,
 iommu@...ts.linux.dev, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 14/14] iommu: Track iopf group instead of last fault

On 1/6/24 1:53 AM, Jason Gunthorpe wrote:
> On Wed, Dec 20, 2023 at 09:23:32AM +0800, Lu Baolu wrote:
>>   /**
>> - * iommu_handle_iopf - IO Page Fault handler
>> - * @fault: fault event
>> - * @iopf_param: the fault parameter of the device.
>> + * iommu_report_device_fault() - Report fault event to device driver
>> + * @dev: the device
>> + * @evt: fault event data
>>    *
>> - * Add a fault to the device workqueue, to be handled by mm.
>> + * Called by IOMMU drivers when a fault is detected, typically in a threaded IRQ
>> + * handler. When this function fails and the fault is recoverable, it is the
>> + * caller's responsibility to complete the fault.
> This patch seems OK for what it does so:
> 
> Reviewed-by: Jason Gunthorpe<jgg@...dia.com>
> 
> However, this seems like a strange design, surely this function should
> just call ops->page_response() when it can't enqueue the fault?
> 
> It is much cleaner that way, so maybe you can take this into a
> following patch (along with the driver fixes to accomodate. (and
> perhaps iommu_report_device_fault() should return void too)
> 
> Also iopf_group_response() should return void (another patch!),
> nothing can do anything with the failure. This implies that
> ops->page_response() must also return void - which is consistent with
> what the drivers do, the failure paths are all integrity validations
> of the fault and should be WARN_ON'd not return codes.

Make sense. I will integrate the code in the next version and convert
iommu_report_device_fault() to return void.

Best regards,
baolu