linux-kernel - Re: [PATCH v13 07/13] iommu/vt-d: Add SVA domain support

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Date:   Fri, 23 Sep 2022 10:07:21 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 07/13] iommu/vt-d: Add SVA domain support

On Fri, Sep 23, 2022 at 08:41:56PM +0800, Baolu Lu wrote:
> On 2022/9/23 20:15, Jason Gunthorpe wrote:
> > On Fri, Sep 23, 2022 at 10:21:51AM +0800, Baolu Lu wrote:
> > 
> > > At the beginning of this project, I wanted to consolidate the mm
> > > notifications into the core. However, ARM SMMUv3 and Intel handle the mm
> > > notifications a little differently. Then I decided to do this work
> > > separately from the current series.
> > 
> > It doesn't look really different..
> 
> They are essentially the same, but slightly different. For example, arm
> smmuv3 provides .free_notifier, and I don't think it could be merged to
> the release callback.

free_notifier allows to use mmu_notifier_put() instead of
mmu_notifier_unregister() which avoids a synchronize_rcu() penalty on
teardown. Intel should copy the same design.

Jason