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Date:   Tue, 12 Dec 2023 11:14:47 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Baolu Lu <baolu.lu@linux.intel.com>
Cc:     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
Message-ID: <20231212151447.GC3013885@ziepe.ca>
References: <20231207064308.313316-1-baolu.lu@linux.intel.com>
 <20231207064308.313316-13-baolu.lu@linux.intel.com>
 <20231211152456.GB1489931@ziepe.ca>
 <416b6639-8904-4b31-973c-d5522e2731d8@linux.intel.com>
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On Tue, Dec 12, 2023 at 01:17:47PM +0800, Baolu Lu wrote:
> 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);
> 
> ?

Not without a synchronize_rcu

disable new PRI reception should be done by the driver - it should
turn off PRI generation in the IOMMU HW and flush any HW PRI queues.

> >   - 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.

Yes

Jason