linux-kernel - Re: [PATCH v6 05/22] iommu: Introduce cache_invalidate API

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Date:   Thu, 21 Mar 2019 15:10:05 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        yi.l.liu@...ux.intel.com, kevin.tian@...el.com,
        vincent.stehle@....com, ashok.raj@...el.com, kvm@...r.kernel.org,
        peter.maydell@...aro.org, marc.zyngier@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, christoffer.dall@....com,
        alex.williamson@...hat.com, robin.murphy@....com,
        kvmarm@...ts.cs.columbia.edu, eric.auger.pro@...il.com,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v6 05/22] iommu: Introduce cache_invalidate API

On Thu, 21 Mar 2019 15:32:45 +0100
Auger Eric <eric.auger@...hat.com> wrote:

> Hi jean, Jacob,
> 
> On 3/21/19 3:13 PM, Jean-Philippe Brucker wrote:
> > On 21/03/2019 13:54, Auger Eric wrote:  
> >> Hi Jacob, Jean-Philippe,
> >>
> >> On 3/20/19 5:50 PM, Jean-Philippe Brucker wrote:  
> >>> On 20/03/2019 16:37, Jacob Pan wrote:
> >>> [...]  
> >>>>> +struct iommu_inv_addr_info {
> >>>>> +#define IOMMU_INV_ADDR_FLAGS_PASID	(1 << 0)
> >>>>> +#define IOMMU_INV_ADDR_FLAGS_ARCHID	(1 << 1)
> >>>>> +#define IOMMU_INV_ADDR_FLAGS_LEAF	(1 << 2)
> >>>>> +	__u32	flags;
> >>>>> +	__u32	archid;
> >>>>> +	__u64	pasid;
> >>>>> +	__u64	addr;
> >>>>> +	__u64	granule_size;
> >>>>> +	__u64	nb_granules;
> >>>>> +};
> >>>>> +
> >>>>> +/**
> >>>>> + * First level/stage invalidation information
> >>>>> + * @cache: bitfield that allows to select which caches to
> >>>>> invalidate
> >>>>> + * @granularity: defines the lowest granularity used for the
> >>>>> invalidation:
> >>>>> + *     domain > pasid > addr
> >>>>> + *
> >>>>> + * Not all the combinations of cache/granularity make sense:
> >>>>> + *
> >>>>> + *         type |   DEV_IOTLB   |     IOTLB     |
> >>>>> PASID    |
> >>>>> + * granularity	|		|		|
> >>>>> cache	|
> >>>>> + *
> >>>>> -------------+---------------+---------------+---------------+
> >>>>> + * DOMAIN	|	N/A	|       Y	|
> >>>>> Y	|
> >>>>> + * PASID	|	Y	|       Y	|
> >>>>> Y	|
> >>>>> + * ADDR		|       Y	|       Y	|
> >>>>> N/A	|
> >>>>> + */
> >>>>> +struct iommu_cache_invalidate_info {
> >>>>> +#define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
> >>>>> +	__u32	version;
> >>>>> +/* IOMMU paging structure cache */
> >>>>> +#define IOMMU_CACHE_INV_TYPE_IOTLB	(1 << 0) /* IOMMU
> >>>>> IOTLB */ +#define IOMMU_CACHE_INV_TYPE_DEV_IOTLB	(1 <<
> >>>>> 1) /* Device IOTLB */ +#define
> >>>>> IOMMU_CACHE_INV_TYPE_PASID	(1 << 2) /* PASID cache */  
> >>>> Just a clarification, this used to be an enum. You do intend to
> >>>> issue a single invalidation request on multiple cache types?
> >>>> Perhaps for virtio-IOMMU? I only see a single cache type in your
> >>>> patch #14. For VT-d we plan to issue one cache type at a time
> >>>> for now. So this format works for us.  
> >>>
> >>> Yes for virtio-iommu I'd like as little overhead as possible,
> >>> which means a single invalidation message to hit both IOTLB and
> >>> ATC at once, and the ability to specify multiple pages with
> >>> @nb_granules.  
> >> The original request/explanation from Jean-Philippe can be found
> >> here: https://lkml.org/lkml/2019/1/28/1497
> >>  
> >>>  
> >>>> However, if multiple cache types are issued in a single
> >>>> invalidation. They must share a single granularity, not all
> >>>> combinations are valid. e.g. dev IOTLB does not support domain
> >>>> granularity. Just a reminder, not an issue. Driver could filter
> >>>> out invalid combinations.  
> >> Sure I will add a comment about this restriction.  
> >>>
> >>> Agreed. Even the core could filter out invalid combinations based
> >>> on the table above: IOTLB and domain granularity are N/A.  
> >> I don't get this sentence. What about vtd IOTLB domain-selective
> >> invalidation:  
> > 
> > My mistake: I meant dev-IOTLB and domain granularity are N/A  
> 
> Ah OK, no worries.
> 
> How do we proceed further with those user APIs? Besides the comment to
> be added above and previous suggestion from Jean ("Invalidations by
> @granularity use field ...), have we reached a consensus now on:
> 
> - attach/detach_pasid_table
> - cache_invalidate
> - fault data and fault report API?
> 
These APIs are sufficient for today's VT-d use and leave enough space
for extension. E.g. new fault reasons.

I have cherry picked the above APIs from your patchset to enable VT-d
nested translation. Going forward, I will reuse these until they get
merged.

> If not, please let me know.
> 
> Thanks
> 
> Eric
> 
> 
> > 
> > Thanks,
> > Jean
> >   
> >> "
> >> • IOTLB entries caching mappings associated with the specified
> >> domain-id are invalidated.
> >> • Paging-structure-cache entries caching mappings associated with
> >> the specified domain-id are invalidated.
> >> "
> >>
> >> Thanks
> >>
> >> Eric
> >>  
> >>>
> >>> Thanks,
> >>> Jean
> >>>  
> >>>>  
> >>>>> +	__u8	cache;
> >>>>> +	__u8	granularity;
> >>>>> +	__u8	padding[2];
> >>>>> +	union {
> >>>>> +		__u64	pasid;
> >>>>> +		struct iommu_inv_addr_info addr_info;
> >>>>> +	};
> >>>>> +};
> >>>>> +
> >>>>> +
> >>>>>  #endif /* _UAPI_IOMMU_H */  
> >>>>
> >>>> [Jacob Pan]
> >>>> _______________________________________________
> >>>> iommu mailing list
> >>>> iommu@...ts.linux-foundation.org
> >>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >>>>  
> >>>  
> >> _______________________________________________
> >> iommu mailing list
> >> iommu@...ts.linux-foundation.org
> >> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >>  
> >   

[Jacob Pan]

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