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

Auger Eric
2019-04-25T13:21:17Z

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
>