Re: [Qemu-devel] [PATCH v3 00/12] Introduce new iommu notifier framework for virt-SVA

[Liu, Yi L]

> From: Peter Xu [mailto:address@hidden
> Sent: Tuesday, March 6, 2018 2:56 PM
> Subject: Re: [PATCH v3 00/12] Introduce new iommu notifier framework for 
> virt-SVA
> 
> On Thu, Mar 01, 2018 at 06:33:23PM +0800, Liu, Yi L wrote:
> > This patchset is to introduce a notifier framework for virt-SVA.
> > You may find virt-SVA design details from the link below.
> >
> > https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg04925.html
> >
> > SVA is short for Shared Virtual Addressing. This is also called Shared
> > Virtual Memory in previous patchsets. However, SVM is confusing as it
> > can also be short for Secure Virtual Machine. So this patchset use
> > Shared Virtual Addressing instead of Shared Virtual Memory. And it
> > would be applied in future (SVA)related patch series as well.
> >
> > Qemu has an existing notifier framework based on MemoryRegion, which
> > are used for MAP/UNMAP. However, it is not well suited for virt-SVA.
> > Reasons are as below:
> > - virt-SVA works along with PT = 1
> > - if PT = 1 IOMMU MR are disabled so MR notifier are not registered
> > - new notifiers do not fit nicely in this framework as they need to be
> >   registered even if PT = 1
> > - need a new framework to attach the new notifiers
> > - Additional background can be got from:
> >   https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg04931.html
> >
> > So a new iommu notifier framework is needed. This patchset introduces
> > a notifier framework based on IOMMUSVAContext. IOMMUSVAContext is
> > introduced to be an abstract of virt-SVA operations in Qemu.
> >
> > Patch Overview:
> > * 1 - 2: rename existing naming, the IOMMU MemoryRegion Notifier
> >          framework
> > * 3 - 4: introduce SVA notifier framework based on IOMMUSVAContext
> > * 5 - 7: introduce PCISVAOps and expose the SVA notfier framework
> >          through hw/pci layer
> > * 8 - 12: show the usage of SVA notifier in Intel vIOMMU emulator
> 
> Do you have online branch so that I can check out?

yes, I should have pasted it. Here it is:
https://github.com/luxis1999/sva_notifier.git

> The patches are a bit scattered and it's really hard for me to
> reference things within it... So a complete tree to read would be
> nice.
> 
> I roughly went over most of the patches, and the framework you
> introduced is still not that clear to me.  For now I feel like it can
> be simplified somehow, but I'll hold and speak after I read the whole
> tree again.
> 
> Also, it'll be good too if you can always provide some status update
> of the kernel-counterpart it.

Good suggestion. For this patchset, it only affects Qemu. Yeah, but for
the whole virt-SVA enabling, there is kernel-counterparts. I would do
it in the virt-SVA patchset series.

Thanks,
Yi Liu