linux-kernel - Re: [RFC PATCH 2/2] iommu: Add IOMMU_UNBIND_FAULT

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Message-ID: <20201016070759.GA12905@infradead.org>
Date:   Fri, 16 Oct 2020 08:07:59 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     dwmw2@...radead.org, baolu.lu@...ux.intel.com, joro@...tes.org,
        zhangfei.gao@...aro.org, wangzhou1@...ilicon.com, arnd@...db.de,
        gregkh@...uxfoundation.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, linux-accelerators@...ts.ozlabs.org,
        kevin.tian@...el.com, jacob.jun.pan@...ux.intel.com,
        ashok.raj@...el.com, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] iommu: Add IOMMU_UNBIND_FAULT_PENDING flag

On Thu, Oct 15, 2020 at 11:00:29AM +0200, Jean-Philippe Brucker wrote:
> IOMMU drivers only need to flush their PRI queue when faults might be
> pending. According to the PCIe spec (quoted below) this only happens
> when using the "Stop Marker" method. Otherwise the function waits for
> pending faults before signaling to the device driver that it can
> unbind().
> 
> Add the IOMMU_UNBIND_FAULT_PENDING flags to unbind(), to tell the IOMMU
> driver whether it's worth flushing the queue.

As we have no code using the "stop marker" method please just remove
the code entirely instead of adding a flag that is just dead code.