RE: [PATCH v2 04/22] hw/iommu: introduce HostIOMMUContext

["Liu, Yi L" <yi.l.liu@intel.com>]

Hi Eric,

> From: Auger Eric < eric.auger@redhat.com>
> Sent: Tuesday, March 31, 2020 1:23 AM
> To: Liu, Yi L <yi.l.liu@intel.com>; qemu-devel@nongnu.org;
> Subject: Re: [PATCH v2 04/22] hw/iommu: introduce HostIOMMUContext
> 
> Yi,
> 
> On 3/30/20 6:24 AM, Liu Yi L wrote:
> > Currently, many platform vendors provide the capability of dual stage
> > DMA address translation in hardware. For example, nested translation
> > on Intel VT-d scalable mode, nested stage translation on ARM SMMUv3,
> > and etc. In dual stage DMA address translation, there are two stages
> > address translation, stage-1 (a.k.a first-level) and stage-2 (a.k.a
> > second-level) translation structures. Stage-1 translation results are
> > also subjected to stage-2 translation structures. Take vSVA (Virtual
> > Shared Virtual Addressing) as an example, guest IOMMU driver owns
> > stage-1 translation structures (covers GVA->GPA translation), and host
> > IOMMU driver owns stage-2 translation structures (covers GPA->HPA
> > translation). VMM is responsible to bind stage-1 translation structures
> > to host, thus hardware could achieve GVA->GPA and then GPA->HPA
> > translation. For more background on SVA, refer the below links.
> >  - https://www.youtube.com/watch?v=Kq_nfGK5MwQ
> >  - https://events19.lfasiallc.com/wp-content/uploads/2017/11/\
> > Shared-Virtual-Memory-in-KVM_Yi-Liu.pdf
> >
[...]
> > +void host_iommu_ctx_init(void *_iommu_ctx, size_t instance_size,
> > +                         const char *mrtypename,
> > +                         uint64_t flags)
> > +{
> > +    HostIOMMUContext *iommu_ctx;
> > +
> > +    object_initialize(_iommu_ctx, instance_size, mrtypename);
> > +    iommu_ctx = HOST_IOMMU_CONTEXT(_iommu_ctx);
> > +    iommu_ctx->flags = flags;
> > +    iommu_ctx->initialized = true;
> > +}
> > +
> > +static const TypeInfo host_iommu_context_info = {
> > +    .parent             = TYPE_OBJECT,
> > +    .name               = TYPE_HOST_IOMMU_CONTEXT,
> > +    .class_size         = sizeof(HostIOMMUContextClass),
> > +    .instance_size      = sizeof(HostIOMMUContext),
> > +    .abstract           = true,
> Can't we use the usual .instance_init and .instance_finalize?
sorry, I somehow missed this comment. In prior patch, .instace_init
was used, but the current major init method is via host_iommu_ctx_init(),
so .instance_init is not really necessary.
https://www.spinics.net/lists/kvm/msg210878.html

Regards,
Yi Liu