Re: [PATCH 2/2] mwait_idle: Broadwell support

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/10/16 22:06, Jan Beulich wrote:
>>>> On 16.10.14 at 14:54, <tiejun.chen@intel.com> wrote:
>> Did you guys validate this in real machine? Or any potential side affect?
>>
>> When I do IGD GFX passthrough with qemu-xen-traditional, I found in the
>> boot phase of VM, the target will reboot. After I revert this everything
>> is fine.
>
> Please be more precise. What is "target" here? Host? Guest?

The real target is BDW based on stepping E. When I use 
qemu-xen-traditional to validate IGD passthrough like this,

gfx_passthru=1
pci=["00:02.0", "00:14.0"]

Here the device at "00:02.0" is IGD device, another is USB controller.

And we should pass 'no-sharept' to disable shared EPT table since you 
know there is a well-know RMRR problem I'm trying to fix.

During the Windows7 guest VM boot phase, the physical machine reboot 
directly.

> Also, reporting issues just verbally (i.e. without any logs or other
> actual technical information) rarely makes a lot of sense.

As I said above the machine reboot directly. I can't see any output.

>
>> Note I don't add anything into codes. Here I just build Xen unstable 4.5
>> to use qemu-xen-traditional. And additionally, my BDW is based on
>> stepping E, and guest is WindXP.

Any other technical information you guys want to know?

>
> But the change is only about C-state handling for a particular
> CPU model. There's really nothing being added that doesn't
> already work fine elsewhere. I.e. this patch being the apparent
> culprit of a problem you see makes it relatively likely that your
> hardware is having some issue.

Yes I also suspect this point but I tried two machine, I still can see 
the same problem. Maybe this is related to CPU stepping, BIOS or some 
errata we may ignore previously. So I just post this to ask if anybody 
know this in detail.

Thanks
Tiejun
>
> Jan
>
>