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Message-ID: <416b6639-8904-4b31-973c-d5522e2731d8@linux.intel.com>
Date:   Tue, 12 Dec 2023 13:17:47 +0800
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Cc:     baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Nicolin Chen <nicolinc@nvidia.com>,
        Yi Liu <yi.l.liu@intel.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Longfang Liu <liulongfang@huawei.com>,
        Yan Zhao <yan.y.zhao@intel.com>, iommu@lists.linux.dev,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 12/12] iommu: Use refcount for fault data access
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To:     Jason Gunthorpe <jgg@ziepe.ca>
References: <20231207064308.313316-1-baolu.lu@linux.intel.com>
 <20231207064308.313316-13-baolu.lu@linux.intel.com>
 <20231211152456.GB1489931@ziepe.ca>
From:   Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <20231211152456.GB1489931@ziepe.ca>
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On 12/11/23 11:24 PM, Jason Gunthorpe wrote:
> Also iopf_queue_remove_device() is messed up - it returns an error
> code but nothing ever does anything with it ???? Remove functions like
> this should never fail.

Yes, agreed.

> 
> Removal should be like I explained earlier:
>   - Disable new PRI reception

This could be done by

	rcu_assign_pointer(param->fault_param, NULL);

?

>   - Ack all outstanding PRQ to the device

All outstanding page requests are responded with
IOMMU_PAGE_RESP_INVALID, indicating that device should not attempt any
retry.

>   - Disable PRI on the device
>   - Tear down the iopf infrastructure
> 
> So under this model if the iopf_queue_remove_device() has been called
> it should be sort of a 'disassociate' action where fault_param is
> still floating out there but iommu_page_response() does nothing.

Yes. All pending requests have been auto-responded.

> IOW pass the refcount from the iommu_report_device_fault() down into
> the fault handler, into the work and then into iommu_page_response()
> which will ultimately put it back.

Yes.

Best regards,
baolu