linux-kernel - Re: [PATCH v8 11/12] iommu: Refine locking for per-device fault data management

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Date:   Mon, 11 Dec 2023 10:50:22 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     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 v8 11/12] iommu: Refine locking for per-device fault data
 management

On Thu, Dec 07, 2023 at 02:43:07PM +0800, Lu Baolu wrote:
> The per-device fault data is a data structure that is used to store
> information about faults that occur on a device. This data is allocated
> when IOPF is enabled on the device and freed when IOPF is disabled. The
> data is used in the paths of iopf reporting, handling, responding, and
> draining.
> 
> The fault data is protected by two locks:
> 
> - dev->iommu->lock: This lock is used to protect the allocation and
>   freeing of the fault data.
> - dev->iommu->fault_parameter->lock: This lock is used to protect the
>   fault data itself.
> 
> Apply the locking mechanism to the fault reporting and responding paths.
> 
> The fault_parameter->lock is also added in iopf_queue_discard_partial().
> It does not fix any real issue, as iopf_queue_discard_partial() is only
> used in the VT-d driver's prq_event_thread(), which is a single-threaded
> path that reports the IOPFs.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> Tested-by: Yan Zhao <yan.y.zhao@...el.com>
> Tested-by: Longfang Liu <liulongfang@...wei.com>
> ---
>  drivers/iommu/io-pgfault.c | 61 +++++++++++++++++++-------------------
>  1 file changed, 30 insertions(+), 31 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason