linux-kernel - Re: [PATCH v2 02/19] iommu: introduce device fault data

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Date:   Thu, 25 Apr 2019 15:21:05 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Yi Liu <yi.l.liu@...el.com>, "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Yi L <yi.l.liu@...ux.intel.com>
Subject: Re: [PATCH v2 02/19] iommu: introduce device fault data

Hi Jean-Philippe,

On 4/25/19 2:46 PM, Jean-Philippe Brucker wrote:
> On 24/04/2019 00:31, Jacob Pan wrote:
>> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
>> new file mode 100644
>> index 0000000..edcc0dd
>> --- /dev/null
>> +++ b/include/uapi/linux/iommu.h
>> @@ -0,0 +1,115 @@
>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>> +/*
>> + * IOMMU user API definitions
>> + */
>> +
>> +#ifndef _UAPI_IOMMU_H
>> +#define _UAPI_IOMMU_H
>> +
>> +#include <linux/types.h>
>> +
>> +#define IOMMU_FAULT_PERM_WRITE	(1 << 0) /* write */
>> +#define IOMMU_FAULT_PERM_EXEC	(1 << 1) /* exec */
>> +#define IOMMU_FAULT_PERM_PRIV	(1 << 2) /* privileged */
> 
> Could we add IOMMU_FAULT_PERM_READ back? The PRI Page Request has both R
> and W fields, and R=W=0 encodes the PASID Stop Markers. Even though the
> IOMMU drivers currently filter out the Stop Markers, we may want to
> inject them into guests at some point in the future, which wouldn't be
> possible with the current API.

OK for me.

 We could add a
> IOMMU_FAULT_PAGE_REQUEST_PERM_VALID bit instead, but I still find it
> weird to denote the validity of a bitfield using a separate bit.
> 
> Given that three different series now rely on this, how about we send
> the fault patches separately for v5.2? I pushed the recoverable fault
> support applied on top of this, with the PERM_READ bit and cleaned up
> kernel doc, to git://linux-arm.org/linux-jpb.git sva/api

my only concern is is it likely to be upstreamed without any actual
user? In the positive, of course, I don't have any objection.

Thanks

Eric
> 
> Thanks,
> Jean
>