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Re: [Xen-devel] [Xen-users] HVM PCI Passthrough: Code 12: Undersized PCI MMIO region?

On 01/06/15 08:00, Pasi Kärkkäinen wrote:
> On Tue, Dec 02, 2014 at 10:08:35PM -0500, Stephen Oberholtzer wrote:
>> All,
> Hello,
>> Please bear with me.  I don't fully understand all of the mechanisms
>> involved here, so this message contains a large quantity of data,
>> including some links to even larger quantities of data.
>> The short version is: I think something isn't reserving enough (GPFN)
>> address space for MMIO.


>> Now, I don't fully understand how this stuff all works, but here's
>> what appears to be happening: Xen isn't reserving enough contiguous
>> GPFN (virtual machine address space) for all of the devices on the
>> virtual PCI bus -- in particular, for what is probably a big honkin'
>> window into the card's onboard RAM.
>> So my two questions are:
>> (1) Is my guess correct?  Or at least close?

I think so.

>> (2) What the heck do I do about it? I don't see any options in
>> xl.cfg(5) for specifying the size of the MMIO region for the virtual
>> PCI bus, or anything similar to that.

There is a new feature in xen 4.5 (soon to be released) that you can
add to the config file (xl.cfg):

   Memory layout
        Specifies the size the MMIO hole below 4GiB will be. Only valid for
        device_model_version = "qemu-xen".

        Cannot be smaller than 256. Cannot be larger than 3840.

        Known good large value is 3072.

Subject: [Xen-devel] Xen Project 4.5 RC4 is Ready Today; Test Day is
Date: Mon, 15 Dec 2014 14:33:33 -0500
From: Russ Pavlicek <russell.pavlicek@xxxxxxxxxxxxxx>
To: xen-devel@xxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxx
<xen-users@xxxxxxxxxxxxx>, xen-announce@xxxxxxxxxxxxxxxxxxxx,
xs-devel@xxxxxxxxxxxxxxxxxxx, mirageos-devel@xxxxxxxxxxxxxxxxxxxx,


This Wednesday, December 17, is our fourth and FINAL Test Day
for the 4.5 release cycle (barring any changes which may result from
Wednesday's Test Day). Release Candidate 4 is available for
assessment today.

If you've held off testing the new release until it matures, delay no
longer!  Test and state your concerns now or the next release you
see could be the official one

Information about testing this release can be found here:

To learn more about Test Days, including the scheduled date
for the final release, check out:

   -Don Slutz

>> NOTE: If I assign 2048MB or less RAM to this VM, the VM crashes at
>> bootup, and has a nasty tendency to take the host with it (lockup).
>> -- 
>> -- Stevie-O
>> Real programmers use COPY CON PROGRAM.EXE
> -- Pasi
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-users
> _______________________________________________
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> http://lists.xen.org/xen-devel

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