Re: [Xen-devel] [RFC] ARM PCI Passthrough design document

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 29/06/17 16:17, Vikram Sethi wrote:
> Hi Julien,
Hi Vikram,

> My thoughts are that while it is not essential to recover from AER and DPC 
> initially, it is critical to at least take the slot offline and notify drivers 
> so they quiesce.
> Without this basic handling, it is possible to create backups in some hardware 
> that result in CPU hangs for loads to adapter MMIO/cfg space and we don't want 
> that.
> i.e it is probably OK to lose the slot/adapter in initial implementation, but 
> IMO it is NOT ok to crash/reboot the system by having watchdog kick in.
> We do need to minimally describe what we will do with the AER and DPC interrupts: are 
> they first handled by Xen and sent as "emulated" interrupt to owning domain?
> Or are the interrupts ignored in initial implementation (not a good idea IMO)?
I don't think it is possible to ask everything to be supported in the 
initial implementation. We have to draw a line so we can get a tech 
preview support in Xen as soon as possible.
At the moment, I am focusing on the foundation that will be required for 
all the boards. I have put them in my low priority tasks because AER, 
DPC, hotplug are optional features and hence not available everywhere.
Feel free to send me a proposal for the design document, patch series if 
you want them to be included in the initial implementation.
> Hotplug also does not need to be solved right away. But we need to at least 
> walk through the flows and convince ourselves we are not painting ourselves in 
> a corner.
> I will be in Budapest for Xen developer summit and we can walk through the ACPI 
> hotplug flow and see how that *could* fit into proposed Xen design.
Glad to know that. Let's schedule some discussions during the summit.

Cheers,

--
Julien Grall

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