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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Feb 17, 2017 at 02:01:15PM -0600, Venu Busireddy wrote:
> On Fri, Feb 17, 2017 at 02:29:32PM -0500, Konrad Rzeszutek Wilk wrote:
> > 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,
> 
> While 'xl dmesg' and the output from the serial console will certainly
> help, it appears that you may have already provided the info needed. There
> may be other devices than 0:02.0 that have problems, but let us assume
> that it is the only device.
> 
> Your change to xen command line is incorrect. The correct option to add
> to the xen command line is:
> 
> rmrr=0x277e28=0:00:02.0

Could you please improve the documentation by mentioning that 'start' and 'end'
should be frame numbers instead of full memory addresses?

I also stumbled upon this and had to go look at the code in order to figure out
what I should pass to rmrr. Also a couple of examples about it's utilization
wouldn't hurt IMHO.

Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel