Re: [Xen-devel] [PATCH v3 0/2] VT-d flush issue

["Xu, Quan" <quan.xu@xxxxxxxxx>]

On 21.12.2015 at 7:47pm, <JBeulich@xxxxxxxx> wrote:
> >>> On 20.12.15 at 14:57, <quan.xu@xxxxxxxxx> wrote:
> > 2. If VT-d is bug, does the hardware_domain continue to work with 
> > PCIe Devices / DRAM well with DMA remapping error?
> >    I think it is no. furthermore, i think VMM can NOT run a normal 
> > HVM domain without device-passthrough.
> 
> In addition to what Andrew said - VT-d is effectively not in use for 
> domains without PT device.

IMO, When VT-d is enabled, but is not working correct. These PCI-e devices 
(Disks/NICs..) DMA/Interrupt behaviors are not predictable. 
Assumed that, VT-d is effectively not in use for domains without PT device, 
while at least the virtualization infrastructure is not trusted.
I think it is also not secure to run PV domains.

> Impacting all such domains by crashing the hypervisor just because (in 
> the extreme case) a single domain with PT devices exhibited a flush 
> issue is a no-go imo.
> 

IMO, a VT-d (IEC/Context/Iotlb) flush issue is not a single domain behavior, it 
is a Hypervisor and infrastructure issue.
ATS device's Device-TLB flush is a single domain issue.
Back to our original goal, my patch set is for ATS flush issue. right?

Quan

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