linux-kernel - Re: [PATCH RFC 10/11] iommu: Make IOPF handling framework generic

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Message-ID: <20220322121520.GB11336@nvidia.com>
Date:   Tue, 22 Mar 2022 09:15:20 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Eric Auger <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 10/11] iommu: Make IOPF handling framework generic

On Tue, Mar 22, 2022 at 01:03:14PM +0800, Lu Baolu wrote:
> On 2022/3/21 20:43, Jason Gunthorpe wrote:
> > On Mon, Mar 21, 2022 at 11:42:16AM +0000, Jean-Philippe Brucker wrote:
> > 
> > > I tend to disagree with that last part. The fault is caused by a specific
> > > device accessing shared page tables. We should keep that device
> > > information throughout the fault handling, so that we can report it to the
> > > driver when things go wrong.
> > SVA faults should never be reported to drivers??
> > 
> 
> When things go wrong, the corresponding response code will be responded
> to the device through iommu_page_response(). The hardware should then
> report the failure to the device driver and the device driver will
> handle it in the device-specific way. There's no need to propagate the
> I/O page faults to the device driver in any case. Do I understand it
> right?

Something like that, I would expect fault failure to be similar to
accessing somethiing that is not in the iommu map. An Error TLP like
thing toward the device and whatever normal device-specific error
propagation happens.

SVA shouldn't require any special support in the using driver beyond
turing on PRI/ATS

Jason