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Message-ID: <b1d361f3-b0ca-7fef-ba31-1bdcdadea96f@redhat.com>
Date: Mon, 6 Jul 2020 15:00:44 +0200
From: Auger Eric <eric.auger@...hat.com>
To: "Liu, Yi L" <yi.l.liu@...el.com>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
"joro@...tes.org" <joro@...tes.org>
Cc: "Tian, Kevin" <kevin.tian@...el.com>,
"jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
"Raj, Ashok" <ashok.raj@...el.com>,
"Tian, Jun J" <jun.j.tian@...el.com>,
"Sun, Yi Y" <yi.y.sun@...el.com>,
"jean-philippe@...aro.org" <jean-philippe@...aro.org>,
"peterx@...hat.com" <peterx@...hat.com>,
"Wu, Hao" <hao.wu@...el.com>,
"stefanha@...il.com" <stefanha@...il.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 02/15] iommu: Report domain nesting info
On 7/6/20 2:20 PM, Liu, Yi L wrote:
> Hi Eric,
>
>> From: Auger Eric <eric.auger@...hat.com>
>> Sent: Monday, July 6, 2020 5:34 PM
>>
>> On 7/4/20 1:26 PM, Liu Yi L wrote:
>>> IOMMUs that support nesting translation needs report the capability info
>> need to report
>>> to userspace, e.g. the format of first level/stage paging structures.
>>>
>>> This patch reports nesting info by DOMAIN_ATTR_NESTING. Caller can get
>>> nesting info after setting DOMAIN_ATTR_NESTING.
>>>
>>> Cc: Kevin Tian <kevin.tian@...el.com>
>>> CC: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>>> Cc: Alex Williamson <alex.williamson@...hat.com>
>>> Cc: Eric Auger <eric.auger@...hat.com>
>>> Cc: Jean-Philippe Brucker <jean-philippe@...aro.org>
>>> Cc: Joerg Roedel <joro@...tes.org>
>>> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
>>> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>>> ---
>>> v3 -> v4:
>>> *) split the SMMU driver changes to be a separate patch
>>> *) move the @addr_width and @pasid_bits from vendor specific
>>> part to generic part.
>>> *) tweak the description for the @features field of struct
>>> iommu_nesting_info.
>>> *) add description on the @data[] field of struct iommu_nesting_info
>>>
>>> v2 -> v3:
>>> *) remvoe cap/ecap_mask in iommu_nesting_info.
>>> *) reuse DOMAIN_ATTR_NESTING to get nesting info.
>>> *) return an empty iommu_nesting_info for SMMU drivers per Jean'
>>> suggestion.
>>> ---
>>> include/uapi/linux/iommu.h | 78
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 78 insertions(+)
>>>
>>> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
>>> index 1afc661..1bfc032 100644
>>> --- a/include/uapi/linux/iommu.h
>>> +++ b/include/uapi/linux/iommu.h
>>> @@ -332,4 +332,82 @@ struct iommu_gpasid_bind_data {
>>> } vendor;
>>> };
>>>
>>> +/*
>>> + * struct iommu_nesting_info - Information for nesting-capable IOMMU.
>>> + * user space should check it before using
>>> + * nesting capability.
>> alignment?
>
> oh, yes, will do it.
>
>>> + *
>>> + * @size: size of the whole structure
>>> + * @format: PASID table entry format, the same definition with
>>> + * @format of struct iommu_gpasid_bind_data.
>> the same definition as struct iommu_gpasid_bind_data @format?
>
> right. yours is much better.
>
>>> + * @features: supported nesting features.
>>> + * @flags: currently reserved for future extension.
>>> + * @addr_width: The output addr width of first level/stage translation
>>> + * @pasid_bits: Maximum supported PASID bits, 0 represents no PASID
>>> + * support.
>>> + * @data: vendor specific cap info. data[] structure type can be deduced
>>> + * from @format field.
>>> + *
>>> + *
>> +===============+===================================================
>> ===+
>>> + * | feature | Notes |
>>> + *
>> +===============+===================================================
>> ===+
>>> + * | SYSWIDE_PASID | PASIDs are managed in system-wide, instead of per |
>>> + * | | device. When a device is assigned to userspace or |
>>> + * | | VM, proper uAPI (userspace driver framework uAPI, |
>>> + * | | e.g. VFIO) must be used to allocate/free PASIDs for |
>>> + * | | the assigned device. |
>>> + * +---------------+------------------------------------------------------+
>>> + * | BIND_PGTBL | The owner of the first level/stage page table must |
>>> + * | | explicitly bind the page table to associated PASID |
>>> + * | | (either the one specified in bind request or the |
>>> + * | | default PASID of iommu domain), through userspace |
>>> + * | | driver framework uAPI (e.g. VFIO_IOMMU_NESTING_OP). |
>>> + * +---------------+------------------------------------------------------+
>>> + * | CACHE_INVLD | The owner of the first level/stage page table must |
>>> + * | | explicitly invalidate the IOMMU cache through uAPI |
>>> + * | | provided by userspace driver framework (e.g. VFIO) |
>>> + * | | according to vendor-specific requirement when |
>>> + * | | changing the page table. |
>>> + * +---------------+------------------------------------------------------+
>> Do you foresee cases where BIND_PGTBL and CACHE_INVLD shouldn't be
>> exposed as features?
>
> sorry, I didn't quite get it. could you explain a little bit more. :-)
For SYSWIDE_PASID I understand SMMU won't advertise it. But do you
foresee any nested implementation not requesting the owner of the tables
to bind and invalidate caches. So I understand those 2 features would
always be supported?
>
>>> + *
>>> + * @data[] types defined for @format:
>>> + *
>> +================================+==================================
>> ===+
>>> + * | @format | @data[] |
>>> + *
>> +================================+==================================
>> ===+
>>> + * | IOMMU_PASID_FORMAT_INTEL_VTD | struct iommu_nesting_info_vtd |
>>> + * +--------------------------------+-------------------------------------+
>>> + *
>>> + */
>>> +struct iommu_nesting_info {
>>> + __u32 size;
>>> + __u32 format;
>>> + __u32 features;
>>> +#define IOMMU_NESTING_FEAT_SYSWIDE_PASID (1 << 0)
>>> +#define IOMMU_NESTING_FEAT_BIND_PGTBL (1 << 1)
>>> +#define IOMMU_NESTING_FEAT_CACHE_INVLD (1 << 2)
>> In other structs the values seem to be defined before the field
>
> not sure. :-) I mimics the below struct from uapi/vfio.h
Yep I noticed that afterwards. In IOMMU uapi it looks the opposite
though. So I would alignto the style in the same file but that's not a
big deal.
>
> struct vfio_iommu_type1_dma_map {
> __u32 argsz;
> __u32 flags;
> #define VFIO_DMA_MAP_FLAG_READ (1 << 0) /* readable from device */
> #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1) /* writable from device */
> __u64 vaddr; /* Process virtual address */
> __u64 iova; /* IO virtual address */
> __u64 size; /* Size of mapping (bytes) */
> };
>
>>> + __u32 flags;
>>> + __u16 addr_width;
>>> + __u16 pasid_bits;
>>> + __u32 padding;
>>> + __u8 data[];
>>> +};
>>> +
>>> +/*
>>> + * struct iommu_nesting_info_vtd - Intel VT-d specific nesting info
>>> + *
>> spurious line
>
> yes, will remove this line.
>
> Regards,
> Yi Liu
>
>>> + *
>>> + * @flags: VT-d specific flags. Currently reserved for future
>>> + * extension.
>>> + * @cap_reg: Describe basic capabilities as defined in VT-d capability
>>> + * register.
>>> + * @ecap_reg: Describe the extended capabilities as defined in VT-d
>>> + * extended capability register.
>>> + */
>>> +struct iommu_nesting_info_vtd {
>>> + __u32 flags;
>>> + __u32 padding;
>>> + __u64 cap_reg;
>>> + __u64 ecap_reg;
>>> +};
>>> +
>>> #endif /* _UAPI_IOMMU_H */
>>>
>> Thanks
>>
>> Eric
>
Thanks
Eric
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