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#1 2016-07-26 15:53:47

newsboost
Member
Registered: 2016-07-24
Posts: 157

Virtualization: Xen - iommu support disappeared after trying xen-4.6

Hi all,

Virtualization with Xen and iommu support has caused me a lot of hours spend, lately. Now I'm beginning to realize the problem. On my new vanilla arch linux I can/could do this:

# dmesg | grep -i iommu
[    1.039960] iommu: Adding device 0000:00:01.0 to group 0
[    1.039980] iommu: Adding device 0000:00:01.1 to group 0
[    1.040311] iommu: Adding device 0000:00:02.0 to group 1
[    1.040708] iommu: Adding device 0000:00:10.0 to group 2
[    1.040780] iommu: Adding device 0000:00:10.1 to group 2
[    1.041107] iommu: Adding device 0000:00:11.0 to group 3
[    1.041440] iommu: Adding device 0000:00:12.0 to group 4
[    1.041452] iommu: Adding device 0000:00:12.2 to group 4
[    1.041788] iommu: Adding device 0000:00:13.0 to group 5
[    1.041801] iommu: Adding device 0000:00:13.2 to group 5
[    1.042142] iommu: Adding device 0000:00:14.0 to group 6
[    1.042155] iommu: Adding device 0000:00:14.2 to group 6
[    1.042167] iommu: Adding device 0000:00:14.3 to group 6
[    1.042565] iommu: Adding device 0000:00:14.4 to group 7
[    1.042897] iommu: Adding device 0000:00:14.5 to group 8
[    1.043293] iommu: Adding device 0000:00:15.0 to group 9
[    1.043365] iommu: Adding device 0000:00:15.2 to group 9
[    1.043718] iommu: Adding device 0000:00:18.0 to group 10
[    1.043732] iommu: Adding device 0000:00:18.1 to group 10
[    1.043746] iommu: Adding device 0000:00:18.2 to group 10
[    1.043759] iommu: Adding device 0000:00:18.3 to group 10
[    1.043773] iommu: Adding device 0000:00:18.4 to group 10
[    1.043788] iommu: Adding device 0000:00:18.5 to group 10
[    1.043798] iommu: Adding device 0000:01:00.0 to group 1
[    1.043808] iommu: Adding device 0000:01:00.1 to group 1
[    1.043994] iommu: Adding device 0000:03:00.0 to group 9
[    1.044012] iommu: Adding device 0000:04:00.0 to group 9
[    1.044013] AMD-Vi: Found IOMMU at 0000:00:00.2 cap 0x40
[   10.670439] AMD IOMMUv2 driver by Joerg Roedel <jroedel@suse.de>

A few lines about my cpu:

# cat /proc/cpuinfo
vendor_id	: AuthenticAMD
cpu family	: 21
model		: 19
model name	: AMD A10-6800B APU with Radeon(tm) HD Graphics
stepping	: 1
microcode	: 0x6001119
cpu MHz		: 2000.000
cache size	: 2048 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 2
apicid		: 19
initial apicid	: 3
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf eagerfpu pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb cpb hw_pstate vmmcall bmi1 arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold
bugs		: fxsave_leak sysret_ss_attrs
bogomips	: 8188.04
TLB size	: 1536 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro

I tried to look here: https://aur.archlinux.org/packages/xen/ for instructions/help/advice. My problem is that when I boot into "Xen mode" (with the corresponding selection in the grub boot menu), it seems like iommu (virtualization support) disappeared!?! If I do that, I will NOT get the output above... In fact it will look like my AMD-cpu don't understand virtualization extensions with the message "AMD IOMMUv2 functionality not available on this system"... So, the exact same hardware. Booting without the xen-entry and IOMMUv2 is possible, but booting WITH the Xen-grub-entry I've made, then the system reports that IOMMUv2 is not available... Weird?!? What is going on?

I used xen-4.6, which I took from https://gitlab.com/johnth/aur-xen/tree/xen-4.6 (because I couldn't find an better new version of Xen for arch)??? I installed dependencies and did used "makepkg" to build followed by "pacman -U xen-4.7.0-1-x86_64.pkg.tar.xz". Everything seemed to work - I could boot and make "xl list" and "xl create" or "xl destroy" etc... I think maybe or probably my problem is related to something about binutils. I think something about this "pep" is incorrect, as you see here:

# ld -V
GNU ld (GNU Binutils) 2.26.1
  Supported emulations:
   elf_x86_64
   elf32_x86_64
   elf_i386
   elf_iamcu
   i386linux
   elf_l1om
   elf_k1om
   i386pep
   i386pe

I believe there should be a line saying something about x86_64pep - am I right? Could this be a reason for why iommu-support under Xen seems to have disappeared? The log files are HUGE for makepkg and searching for "iommu" just gives a LOT of hints. So I don't know where to start, except first I would like to ask if I'm right that there's a problem with binutils and I believe for my system I should have a line with x86_64pep or similar... Please confirm if this is correct.

In any case, I hope one/some of you have a few hints or good advice for me, thanks!

Last edited by newsboost (2016-07-26 20:51:47)

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