[vfio-users] regression from linux 4.0.4 to 4.2.0

[Okky Hendriansyah]

Hi Alex,

I have experienced my setup is also not working as it used to after upgrading from 4.1.6 to 4.2.1. After reading on the list mentioned I googled around and found [1].

Changing my processor and memory settings from -smp cpus=8,cores=4,threads=2,sockets=1 -m size=16G to -smp cpus=4,cores=4,threads=1,sockets=1 -m size=8G resulting the VM successfully boots like normal. But changing to other values did not always succeeded. I did not now the formula so I kind of brute forcing my way. I think I managed to boot the VM also with -smp cpus=8,cores=4,threads=2,sockets=1 -m size=4G. I forgot the details.

Currently I’m rolling back to 4.1.6, but if there’s something that I could provide to help finding out the issue, I can upgrade it and test it again. Please let me know.

[1] https://github.com/tianocore/edk2/issues/21

-- 
Okky Hendriansyah
On September 28, 2015 at 23:53:08, globalgorrilla at fastmail.fm (globalgorrilla at fastmail.fm) wrote:

Alex,

I reported this on 08/18. It's been echoed several times on this list  
since.

You've said everything is working for you and you appear to have a very  
similar setup to us others (passing through devices with VFIO to QEMU  
and using OVMF).

Circumstantial evidence is that there is something in > 4.1 that (often)  
breaks OVMF in QEMU.

How could we dig into this? Perhaps it's not related to vfio?

Regarding the MTRR patch, I had made the fix myself in the 4.2 RCs and I  
believe the patch is merged in already to 4.2 +. I don't think that is  
the culprit ...?

Thoughts?

On 20 Sep 2015, at 9:09, Kővágó Zoltán wrote:

> Hello,
>
> I've been using vfio-pci to passthrough a GPU to virtual machine since  
> some time now, and it worked great. But this weekend I've finally had  
> enough time to update kernel, and things are completely broken with  
> the new kernel...
>
> I've been using the ACS override patch (and a quick-and-dirty fix for  
> multiple GOPs, but created a proper-ish patch yesterday, see  
> http://article.gmane.org/gmane.linux.kernel.efi/6332 ), CSM disabled  
> in UEFI and using OVMF virtual machines. The motherboard is an ASRock  
> Z87M Extreme4, with two PCI video cards (an NVidia GT640 (the primary  
> card, used for linux), for which I almost had to beg at Gigabyte  
> support to send an UEFI compatible VBIOS, and a GTX980 (secondary  
> card, to passthrough)). The integrated Intel GPU is diabled in UEFI  
> settings. I'm not sure if it's supposed to work, but with 4.0.4  
> kernels it worked like a charm.
>
> Now with 4.2.0, when I start qemu the monitor attached to the  
> secondary card powers down, and then nothing happens, except qemu  
> eating about 150% cpu. I've started bisecting the kernel, and found  
> out that
>
> d69afbc6b1b5d0579f13d1a6339d952c4f60a9f4 KVM: MMU: fix decoding cache  
> type from MTRR
>
> is the culprit. When mtrr is diabled, the old code returns 0xFF while  
> the new returns MTRR_TYPE_UNCACHABLE. I have absolutely no idea what  
> the hell is going on here, but changing that return statement back  
> solves the problem, until
>
> b18d5431acc7a2fd22767925f3a6f597aa4bd29e KVM: x86: fix CR0.CD  
> virtualization
>
> If I comment out the if kvm_read_cd0 part it will work.. until  
> 4e241557fc1cb560bd9e77ca1b4a9352732a5427, which is a merge commit(!).  
> I'm attaching a patch, it fixes the problem until  
> f2ae45edbca7ba5324eef01719ede0151dc5cead for me. But as I said  
> earlier I have no freakin' idea what's going on here.
>
> I have recompiled OVMF from svn yesterday evening, and have a  
> recent-ish qemu master (with some audio related patches). Tell me if  
> you need any more information.
>
> Thanks,
> Zoltan
>
> [magic.patch]
> _______________________________________________
> vfio-users mailing list
> vfio-users at redhat.com
> https://www.redhat.com/mailman/listinfo/vfio-users

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