Re: [PATCH v5 08/14] iommufd/viommu: Add iommufd_viommu_report_event helper

On Tue, Jan 21, 2025 at 01:40:05PM -0800, Nicolin Chen wrote:

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There is also the minor detail of what happens if the hypervisor HW queue overflows - I don't know the answer here. It is security concerning since the VM can spam DMA errors at high rate. :|

In my view, the hypervisor queue is the vHW queue for the VM, so it should act like a HW, which means it's up to the guest kernel driver that handles the high rate DMA errors..

I'm mainly wondering what happens if the single physical kernel event queue overflows because it is DOS'd by a VM and the hypervisor cannot drain it fast enough?

I haven't looked closely but is there some kind of rate limiting or otherwise to mitigate DOS attacks on the shared event queue from VMs?

Jason