CentOS 8 as a Xen PV Guest

[ChrisE]

Has anyone managed to get CentOS 8 running as a Xen PV guest?

In my testing the kernel flat out fails to launch off pygrub, so has RedHat removed all Xen support from RHEL8 including PV_Ops/DomU?

xc: error: panic: xc_dom_core.c:702: xc_dom_find_loader: no loader found: Invalid kernel
libxl: error: libxl_dom.c:721:libxl__build_dom: xc_dom_parse_image failed: No such file or directory

[rumcho]

I'm having the exact same issue. And I see no "xen" directory anywhere on the new CentOS 8 tree.

[regex]

I had the same issue while looking into building a new xen PV template for CentOS 8. Pygrub seems incompatible with the new Grub2 configuration in CentOS 8. The kernels are not listed anymore in grub.cfg so pygrub can't parse them.

[regex]

Quick follow up, you can make pygrub working again by disabling grub2 BLS in el8:

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sed -i 's/^GRUB_ENABLE_BLSCFG=.*/GRUB_ENABLE_BLSCFG=false/' /etc/default/grub
grub2-mkconfig -o /boot/grub2/grub.cfg

EL8 would still need this patch that has been added to Fedora 30: https://bugzilla.redhat.com/attachment. ... ction=diff

[Grepknowledge]

Same issue here , trying to make Centos8 work under XEN PV , still doesn't boot and showing this exact log error

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xc: error: panic: xc_dom_core.c:702: xc_dom_find_loader: no loader found: Invalid kernel

[burnley]

Stock CentOS 8 kernel doesn't boot as either PV or PVH, only as HVM. But managed to boot the domU as PVH using kernel-ml from ELRepo, currently running 5.3.8-1.el8.elrepo.x86_64. When booted as PV it crashes:

[ 5.772001] BUG: unable to handle page fault for address: ffffc900401f7818
[ 5.772023] #PF: supervisor read access in kernel mode
[ 5.772035] #PF: error_code(0x0000) - not-present page
[ 5.772047] PGD bc9d6067 P4D bc9d6067 PUD fd2c067 PMD fd2d067 PTE 0
[ 5.772062] Oops: 0000 [#1] SMP NOPTI
[ 5.772073] CPU: 1 PID: 596 Comm: systemd-udevd Not tainted 5.3.8-1.el8.elrepo.x86_64 #1
[ 5.772091] RIP: e030:pmc_core_probe+0x13a/0x2c0 [intel_pmc_core]
[ 5.772105] Code: c0 48 c7 c6 ab 01 19 c0 48 8d 7d 28 e8 5f c3 f9 c0 48 8b 05 a8 48 00 00 48 89 ab 88 00 00 00 48 63 40 44 48 03 05 8e 48 00 00 <8b> 00 48 8b 15 8d 48 00 00 48 c7 c7 c0 0b 19 c0 8b 4a 48 ba 01 00
[ 5.772142] RSP: e02b:ffffc900402afaf0 EFLAGS: 00010286
[ 5.772155] RAX: ffffc900401f7818 RBX: ffffffffc0199000 RCX: 0000000002ffffff
[ 5.772527] RDX: ffffffffc01944c0 RSI: ffffffffc01901ab RDI: ffffffffc0194508
[ 5.772911] RBP: ffffffffc01944e0 R08: ffffc900401f6000 R09: ffffc900401f6000
[ 5.773290] R10: 0000000000007ff0 R11: ffff888006736420 R12: ffffffffc0194028
[ 5.773676] R13: ffffffffc0194028 R14: 0000000000000008 R15: ffffffffc0199000
[ 5.774069] FS: 00007f106c336940(0000) GS:ffff8880bc100000(0000) knlGS:0000000000000000
[ 5.774464] CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5.774860] CR2: ffffc900401f7818 CR3: 00000000b78c4000 CR4: 0000000000040660
[ 5.775288] Call Trace:
[ 5.775690] platform_drv_probe+0x35/0x80
[ 5.776088] really_probe+0xef/0x390
[ 5.776489] ? driver_allows_async_probing+0x50/0x50
[ 5.776887] driver_probe_device+0xb4/0x100
[ 5.777277] ? driver_allows_async_probing+0x50/0x50
[ 5.777675] bus_for_each_drv+0x75/0xc0
[ 5.778096] __device_attach+0xd4/0x160
[ 5.778491] bus_probe_device+0x87/0xa0
[ 5.778863] device_add+0x40f/0x660
[ 5.779229] platform_device_add+0x10e/0x240
[ 5.779605] ? 0xffffffffc01cc000
[ 5.779975] do_one_initcall+0x46/0x1f4
[ 5.780357] ? _cond_resched+0x15/0x30
[ 5.780722] ? kmem_cache_alloc_trace+0x14c/0x220
[ 5.781087] do_init_module+0x5a/0x220
[ 5.781452] load_module+0x179d/0x1930
[ 5.781807] ? __do_sys_init_module+0x141/0x190
[ 5.782157] ? _cond_resched+0x15/0x30
[ 5.782509] __do_sys_init_module+0x141/0x190
[ 5.782851] do_syscall_64+0x5f/0x1f0
[ 5.783189] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 5.783532] RIP: 0033:0x7f106af2a4ae
[ 5.783862] Code: 48 8b 0d dd 09 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 af 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d aa 09 2c 00 f7 d8 64 89 01 48
[ 5.784875] RSP: 002b:00007ffe5fc85768 EFLAGS: 00000246 ORIG_RAX: 00000000000000af
[ 5.785212] RAX: ffffffffffffffda RBX: 000055c89ecbf9b0 RCX: 00007f106af2a4ae
[ 5.785549] RDX: 00007f106ba9680d RSI: 0000000000001dd0 RDI: 000055c89f5310a0
[ 5.785887] RBP: 00007f106ba9680d R08: 000055c89ecb33a0 R09: 0000000000000003
[ 5.786225] R10: 0000000000000004 R11: 0000000000000246 R12: 000055c89f5310a0
[ 5.786575] R13: 000055c89ecb4310 R14: 0000000000020000 R15: 0000000000000000
[ 5.786913] Modules linked in: intel_pmc_core_pltdrv(+) intel_pmc_core crct10dif_pclmul crc32_pclmul xen_fbfront(+) syscopyarea sysfillrect sysimgblt ghash_clmulni_intel joydev fb_sys_fops pcspkr xen_kbdfront intel_rapl_perf ip_tables ext4 mbcache jbd2 xen_netfront xen_blkfront crc32c_intel
[ 5.787945] CR2: ffffc900401f7818
[ 5.788292] ---[ end trace a3f64be860281e19 ]---
[ 5.788629] RIP: e030:pmc_core_probe+0x13a/0x2c0 [intel_pmc_core]
[ 5.788971] Code: c0 48 c7 c6 ab 01 19 c0 48 8d 7d 28 e8 5f c3 f9 c0 48 8b 05 a8 48 00 00 48 89 ab 88 00 00 00 48 63 40 44 48 03 05 8e 48 00 00 <8b> 00 48 8b 15 8d 48 00 00 48 c7 c7 c0 0b 19 c0 8b 4a 48 ba 01 00

[SteffanCline]

I was able to boot my VM as HVM to make the changes and applied the patch as suggested.

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sed -i 's/^GRUB_ENABLE_BLSCFG=.*/GRUB_ENABLE_BLSCFG=false/' /etc/default/grub
grub2-mkconfig -o /boot/grub2/grub.cfg

I installed CentOS 8 in a single partition just to minimize the possibility of issues. I changed the config back to PV and started the guest. No matter what I try, it always goes to the grubdom> prompt. I'm not sure where to go from there. Below is my config

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memory = 24576
maxmem = 24576
vcpus = 8
name = 'test'
vif = [ 'ip=x.x.x.x,mac=00:16:3e:BF:EE:2A,bridge=xenbr0','ip=x.x.x.x,mac=00:16:3e:BF:EE:2B,bridge=xenbr1' ]
address = 'x.x.x.x'
netmask = '255.255.255.0'
disk = ['phy:/dev/vg_h1/test_img,xvda1,w']
boot = 'dc'
on_reboot = 'restart'
on_crash = 'restart'
kernel = "/usr/lib64/xen/boot/pv-grub-x86_64.gz"
extra = "(hd0)/boot/grub2/grub.conf"
vnc = 1
vnclisten = "0.0.0.0"
vncunused = 1
vfb = ['type=vnc,vncunused=1,vncpasswd=xokspfky,vnclisten=0.0.0.0']
vncpasswd = "test"