Re: [Xen-devel] Unable to boot Xen 4.8 with iommu=0

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Feb 17, 2017 at 12:27:25PM -0700, Tamas K Lengyel wrote:
> On Fri, Feb 17, 2017 at 11:56 AM, Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx> wrote:
> > . snip..
> >> >> > Given this commit is pretty old, I'm also curious why it's only 
> >> >> > reported
> >> >> > on 4.8. Tamas, did you succeed with iommu=0 pre 4.8, or 4.8 happens
> >> >> > to be the one upon which you first tried iommu=0 on a platform 
> >> >> > supporting
> >> >> > interrupt remapping?
> >> >>
> >> >> It just happens to be the one I tried. VT-d was spamming my console
> >> >> with faults like this:
> >> >>
> >> >> (XEN) [VT-D]DMAR:[DMA Write] Request device [0000:00:02.0] fault addr
> >> >> 277e28000, iommu reg = ffff82c000201000
> ffff82c000201000
> >> >> (XEN) [VT-D]DMAR: reason 05 - PTE Write access is not set
> >> >>
> >> >> So I figured I can just turn it off to clean up my console. I still
> >> >> don't know what these VT-d faults are about..
> >> >
> >> > What is the 0:02.0 device? Is it being passed in to your guest?
> >>
> >> Nope, there is no pass-through to any guests. The device is:
> >>
> >> 00:02.0 Display controller: Intel Corporation 2nd Generation Core
> >> Processor Family Integrated Graphics Controller (rev 09)
> >
> > Let me guess, you have an SandyBridge motherboard and were using
> > Intel AMT?
> 
> Correct.
> 
> >
> > I see those all the time on that box (and I think my Haswell
> > one too). The best I could narrow it down was that the card decided that
> > certain area should be in the RMRR regions. With Venu/Elen's patch
> > in (see 431685e8deb660976d8e986c41a647944e410c6c) you should be able
> > to provide an rmrr paramater to include these addresses.
> 
> Some more information on how to use that flag would be valuable.. I
> tried "rmrr=270000000-280000000=00:02.0" to no avail and I really have
> no idea what I'm doing here =)

CC-ing Elena and Venu who I hope can help you with this.

You may want to provide the full 'xl dmesg' as the 'rmrr' should have
outputted some details..
> 
> Tamas

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