Re: memory overcomittment with sr-iov device assighment

[Alex Nln <alex.nlnnfn@xxxxxxxxx>]

------- Original Message -------
On Tuesday, June 7th, 2022 at 3:04 AM, Andrew Cooper 
<Andrew.Cooper3@xxxxxxxxxx> wrote:
> But IOMMU violations are not restartable. We can't just take an IOMMU
> fault, and shuffle the guests memory, because the PCIe protocol has
> timeouts. These aren't generally long enough to even send an interrupt
> to request software help, let alone page one part out and another part in.
>
> For an IOMMU mapping to exists, it must point at real RAM, because any
> DMA targetting it cannot be paused and delayed for later.
>

Thanks for the information!

Speaking about IOMMU. Can Xen emulate virtual IOMMU? Just thinking out loud.
If Xen exposes a virtual IOMMU to a guest VM, wouldn't it be possible
for the hypervisor to pin VM's pages that are mapped (dynamically)
by the guest virtual IOMMU? But I guess it will eliminate the performance
benefits of direct device assignment.