Re: Xen virtual IOMMU high level design doc V3

[Lan Tianyu <tianyu.lan@intel.com>]

On 2016年11月22日 18:24, Jan Beulich wrote:
>>>> On 17.11.16 at 16:36, <tianyu.lan@intel.com> wrote:
>> 2) Build ACPI DMAR table in toolstack
>> Now tool stack can boot ACPI DMAR table according VM configure and pass
>> though it to hvmloader via xenstore ACPI PT channel. But the vIOMMU MMIO
>> region is managed by Qemu and it's need to be populated into DMAR
>> table. We may hardcore an address in both Qemu and toolstack and use the 
>> same address to create vIOMMU and build DMAR table.
> 
> Let's try to avoid any new hard coding of values. Both tool stack
> and qemu ought to be able to retrieve a suitable address range
> from the hypervisor. Or if the tool stack was to allocate it, it could
> tell qemu.
> 
> Jan
> 

Hi Jan:
The address range is allocated by Qemu or toolstack and pass to
hypervisor when create vIOMMU. The vIOMMU's address range should be
under PCI address sapce and so we need to reserve a piece of PCI region
for vIOMMU in the toolstack. Then, populate base address in the vDMAR
table and tell Qemu the region via new xenstore interface if we want to
create vIOMMU in the Qemu dummy hypercall wrapper.

Another point, I am not sure whether we can create/destroy vIOMMU
directly in toolstack because virtual device models usually are handled
by Qemu. If yes, we don't need new Xenstore interface. In this case, the
dummy vIOMMU in Qemu will just cover L2 translation for virtual device.

-- 
Best regards
Tianyu Lan

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