Re: [RFC v3 01/21] iommu: Introduce set_pasid_table API

[Jean-Philippe Brucker]

On 25/01/2019 08:55, Auger Eric wrote:
> Hi Jean-Philippe,
> 
> On 1/25/19 9:39 AM, Auger Eric wrote:
>> Hi Jean-Philippe,
>>
>> On 1/11/19 7:16 PM, Jean-Philippe Brucker wrote:
>>> On 08/01/2019 10:26, Eric Auger wrote:
>>>> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
>>>>
>>>> In virtualization use case, when a guest is assigned
>>>> a PCI host device, protected by a virtual IOMMU on a guest,
>>>> the physical IOMMU must be programmed to be consistent with
>>>> the guest mappings. If the physical IOMMU supports two
>>>> translation stages it makes sense to program guest mappings
>>>> onto the first stage/level (ARM/VTD terminology) while to host
>>>> owns the stage/level 2.
>>>>
>>>> In that case, it is mandated to trap on guest configuration
>>>> settings and pass those to the physical iommu driver.
>>>>
>>>> This patch adds a new API to the iommu subsystem that allows
>>>> to set the pasid table information.
>>>>
>>>> A generic iommu_pasid_table_config struct is introduced in
>>>> a new iommu.h uapi header. This is going to be used by the VFIO
>>>> user API. We foresee at least two specializations of this struct,
>>>> for PASID table passing and ARM SMMUv3.
>>>
>>> Last sentence is a bit confusing. With SMMUv3 it is also used for the
>>> PASID table, even when it only has one entry and PASID is disabled.
>> OK removed
>>>
>>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
>>>> Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
>>>> Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
>>>> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
>>>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>>>
>>>> ---
>>>>
>>>> This patch generalizes the API introduced by Jacob & co-authors in
>>>> https://lwn.net/Articles/754331/
>>>>
>>>> v2 -> v3:
>>>> - replace unbind/bind by set_pasid_table
>>>> - move table pointer and pasid bits in the generic part of the struct
>>>>
>>>> v1 -> v2:
>>>> - restore the original pasid table name
>>>> - remove the struct device * parameter in the API
>>>> - reworked iommu_pasid_smmuv3
>>>> ---
>>>>  drivers/iommu/iommu.c      | 10 ++++++++
>>>>  include/linux/iommu.h      | 14 +++++++++++
>>>>  include/uapi/linux/iommu.h | 50 ++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 74 insertions(+)
>>>>  create mode 100644 include/uapi/linux/iommu.h
>>>>
>>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>>> index 3ed4db334341..0f2b7f1fc7c8 100644
>>>> --- a/drivers/iommu/iommu.c
>>>> +++ b/drivers/iommu/iommu.c
>>>> @@ -1393,6 +1393,16 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(iommu_attach_device);
>>>>  
>>>> +int iommu_set_pasid_table(struct iommu_domain *domain,
>>>> +			  struct iommu_pasid_table_config *cfg)
>>>> +{
>>>> +	if (unlikely(!domain->ops->set_pasid_table))
>>>> +		return -ENODEV;
>>>> +
>>>> +	return domain->ops->set_pasid_table(domain, cfg);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(iommu_set_pasid_table);
>>>> +
>>>>  static void __iommu_detach_device(struct iommu_domain *domain,
>>>>  				  struct device *dev)
>>>>  {
>>>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>>>> index e90da6b6f3d1..1da2a2357ea4 100644
>>>> --- a/include/linux/iommu.h
>>>> +++ b/include/linux/iommu.h
>>>> @@ -25,6 +25,7 @@
>>>>  #include <linux/errno.h>
>>>>  #include <linux/err.h>
>>>>  #include <linux/of.h>
>>>> +#include <uapi/linux/iommu.h>
>>>>  
>>>>  #define IOMMU_READ	(1 << 0)
>>>>  #define IOMMU_WRITE	(1 << 1)
>>>> @@ -184,6 +185,7 @@ struct iommu_resv_region {
>>>>   * @domain_window_disable: Disable a particular window for a domain
>>>>   * @of_xlate: add OF master IDs to iommu grouping
>>>>   * @pgsize_bitmap: bitmap of all possible supported page sizes
>>>> + * @set_pasid_table: set pasid table
>>>>   */
>>>>  struct iommu_ops {
>>>>  	bool (*capable)(enum iommu_cap);
>>>> @@ -226,6 +228,9 @@ struct iommu_ops {
>>>>  	int (*of_xlate)(struct device *dev, struct of_phandle_args *args);
>>>>  	bool (*is_attach_deferred)(struct iommu_domain *domain, struct device *dev);
>>>>  
>>>> +	int (*set_pasid_table)(struct iommu_domain *domain,
>>>> +			       struct iommu_pasid_table_config *cfg);
>>>> +
>>>>  	unsigned long pgsize_bitmap;
>>>>  };
>>>>  
>>>> @@ -287,6 +292,8 @@ extern int iommu_attach_device(struct iommu_domain *domain,
>>>>  			       struct device *dev);
>>>>  extern void iommu_detach_device(struct iommu_domain *domain,
>>>>  				struct device *dev);
>>>> +extern int iommu_set_pasid_table(struct iommu_domain *domain,
>>>> +				 struct iommu_pasid_table_config *cfg);
>>>>  extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
>>>>  extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
>>>>  extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
>>>> @@ -696,6 +703,13 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
>>>>  	return NULL;
>>>>  }
>>>>  
>>>> +static inline
>>>> +int iommu_set_pasid_table(struct iommu_domain *domain,
>>>> +			  struct iommu_pasid_table_config *cfg)
>>>> +{
>>>> +	return -ENODEV;
>>>> +}
>>>> +
>>>>  #endif /* CONFIG_IOMMU_API */
>>>>  
>>>>  #ifdef CONFIG_IOMMU_DEBUGFS
>>>> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
>>>> new file mode 100644
>>>> index 000000000000..7a7cf7a3de7c
>>>> --- /dev/null
>>>> +++ b/include/uapi/linux/iommu.h
>>>> @@ -0,0 +1,50 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>>>> +/*
>>>> + * IOMMU user API definitions
>>>> + *
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>
>>> I don't think we need both the boilerplate and the SPDX header
>> OK I only kept the SPDX header.
>>>
>>>> + */
>>>> +
>>>> +#ifndef _UAPI_IOMMU_H
>>>> +#define _UAPI_IOMMU_H
>>>> +
>>>> +#include <linux/types.h>
>>>> +
>>>> +/**
>>>> + * SMMUv3 Stream Table Entry stage 1 related information
>>>> + * @abort: shall the STE lead to abort
>>>> + * @s1fmt: STE s1fmt field as set by the guest
>>>> + * @s1dss: STE s1dss as set by the guest
>>>> + * All field names match the smmu 3.0/3.1 spec (ARM IHI 0070A)
>>>
>>> Not really the case for @abort. Could you clarify whether @abort is
>>> valid in combination with @bypass?
>>> abort corresponds to !Config[2]. In that case the spec says "report
>> abort to device, no event recorded". S1 bypass corresponds to
>> Config=0b1x0. What about removing abort in the SMMUv3 specific part and
>> encode the stage state in the generic part. See below proposal ...
>>>> + */
>>>> +struct iommu_pasid_smmuv3 {
>>>> +	__u8 abort;
>>>> +	__u8 s1fmt;
>>>> +	__u8 s1dss;
>>>> +};
>>>> +
>>>> +/**
>>>> + * PASID table data used to bind guest PASID table to the host IOMMU
>>>> + * Note PASID table corresponds to the Context Table on ARM SMMUv3.
>>>> + *
>>>> + * @version: API version to prepare for future extensions
>>>> + * @format: format of the PASID table
>>>> + *
>>>> + */
>>>> +struct iommu_pasid_table_config {
>>>> +#define PASID_TABLE_CFG_VERSION_1 1
>>>> +	__u32	version;
>>>> +#define IOMMU_PASID_FORMAT_SMMUV3	(1 << 0)
>>>> +	__u32	format;
>>>> +	__u64	base_ptr;
>>>> +	__u8	pasid_bits;
>>>> +	__u8	bypass
>> #define IOMMU_PASID_STREAM_ABORT  (1 << 0)
>> #define IOMMU_PASID_STREAM_BYPASS (1 << 1)
>> #define IOMMU_PASID_STREAM_TRANSLATE (1 << 2)
>> __u8 config;
> Sorry for the confusion, we don't want a bitfield here as those values
> are exclusive.
> 
> What about:
> struct iommu_pasid_table_config {
> #define PASID_TABLE_CFG_VERSION_1 1
>         __u32   version;
> #define IOMMU_PASID_FORMAT_SMMUV3       (1 << 0)
>         __u32   format;
>         __u64   base_ptr;
>         __u8    pasid_bits;
> #define IOMMU_PASID_CONFIG_BYPASS       1
> #define IOMMU_PASID_CONFIG_ABORT        2
> #define IOMMU_PASID_CONFIG_TRANSLATE    3

Yes, this makes more sense :)

>         __u8    config;
>         __u8    padding[6];
>         union {
>                 struct iommu_pasid_smmuv3 smmuv3;
>         };
> };

Thanks,
Jean

> 
> Thanks
> 
> Eric
>>>
>>> We need some padding, in case someone adds a new struct to the union
>>> that requires 64-byte alignment
>> OK
>>>
>>> And 'bypass' might not be the right name if we're making it common,
>>> maybe 'reset' would be clearer? Or we just need to explain that bypass
>>> is the initial state of a nesting domain
>> I will add such comment. To me the "bypass" terminology sounds clearer
>> than "reset"
>>>
>>> Thanks,
>>> Jean
>>>
>>>> +	union {
>>>> +		struct iommu_pasid_smmuv3 smmuv3;
>>>> +	};
>>>> +};
>>>> +
>>>> +#endif /* _UAPI_IOMMU_H */
>>>>
>>>