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Re: [Xen-devel] [Q] Is qemu used when we use VTd?

On Wed, 24 Sep 2008 16:57:21 +0800
"Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> > By the way, Can we recover error condition by only FLR? Resetting link
> > from root port is needed on some error, isn't it?
> Yes, root port link reset is needed for host side. I mean FLR is
> just for guest specific.
> what I'm considering is add error handling to pciback, so that when
> host reset the hierarchy, the pciback's error handler will be
> invoked and notifiy control panel. But I'm not sure still if there
> are any mechanism exists for the notification (otherwise, we need
> xen special mechanism).

We can use "error_detected" interface between AER driver and pciback
driver, can't we? Actually, there is no AER driver in
linux-2.6.18-xen.hg. We have to wait to merge dom0 function into
upstream linux.

The interface between pciback and xend is xen's special mechanism.

> Also not sure if the long latency is
> acceptable for error handling, especially it may finished after
> reset link.

I'm not sure too.

> > I agree with you that implementing full PCI-E future in guest side
> > will be complex. I don't think VT/TC in guest side is needed. But, AER
> I remember I saw a doc that Windows has VC/TC support for HD Audio,
> although not sure how is implemented. Is VC/TC needed for communication
> usage?

I do NOT think VT/TC in guest side is needed.

> > in guest side is required in the long term, because guest OS will be
> > able to handle AER and recover error condition.
> Yes, agree that if guest can do AER, it will enahnce reliability and
> availability. But more elegant design is needed. For example, if
> guest decide that the AER need root port reset link (switch link
> reset should be ok unless SR-IOV), what shall host do?  If host act
> according to guest's suggestion, that may not be safe, I suspect.

I agree with you.  Host should NOT act according to guest's
suggestion. I think host should recover error condition with dom0
linux's AER driver. AER emulation for guest is needed to make guest

> BTW, do you know what will recover action usually be? I didn't find
> much document on it, and the PCI-E spec didn't give much clue
> either.

Linux's AER driver will help us to understand recover
action. Following function is the main logic.



Yuji Shimada

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