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

[Auger Eric]

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


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 */
>>>
>>