Garbage artifacts on VMs windows with low memory allocated

[bnvk]

This is reported to me by a Qubes user- they often see visual screen artifacts contained to one window such as this:

The hardware they are running is:

Model: Lenovo x250
CPU: i3-5010U
RAM: 8 GB

Despite the screenshot being a TemplateVM, they report that is often happens in whereby they have allocated smaller amount of memory to a VM. Here is another example generated in a sys-usb VM

To generate this they did:

• open a gnome-terminal
• pipe urandom to base64 to generate a bunch of text output
• open a bunch of tabs repeatedly

Here is a backtrace on doing this action:

[113188.051925] WARNING: CPU: 0 PID: 0 at /home/user/rpmbuild/BUILD/kernel-4.1.13/linux-4.1.13/drivers/gpu/drm/i915/intel_display.c:10100 intel_check_page_flip+0xd1/0xe0 [i915]()
[113188.051928] Kicking stuck page flip: queued at 5996086, now 5996091
[113188.051930] Modules linked in: loop ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables mmc_block ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw rtsx_pci_ms rtsx_pci_sdmmc snd_hda_codec_realtek mmc_core snd_hda_codec_hdmi memstick snd_hda_codec_generic snd_hda_intel snd_hda_controller iTCO_wdt intel_rapl snd_hda_codec iTCO_vendor_support iosf_mbi snd_hda_core x86_pkg_temp_thermal iwlwifi coretemp snd_hwdep snd_seq joydev snd_seq_device cfg80211 serio_raw i2c_i801 pcspkr rtsx_pci snd_pcm thinkpad_acpi rfkill wmi tpm_tis tpm mei_me
[113188.051969]  snd_timer e1000e snd soundcore ptp lpc_ich mei shpchp pps_core mfd_core xenfs xen_privcmd dm_crypt crct10dif_pclmul crc32_pclmul crc32c_intel i915 i2c_algo_bit drm_kms_helper ehci_pci ehci_hcd drm video xen_acpi_processor xen_pciback xen_netback xen_blkback
[113188.051992] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.1.13-8.pvops.qubes.x86_64 #1
[113188.051994] Hardware name: LENOVO 20CMCTO1WW/20CMCTO1WW, BIOS N10ET36W (1.15 ) 06/19/2015
[113188.051997]  0000000000000000 fb2dd11177b919bc ffff88013f803ce8 ffffffff8176baff
[113188.052001]  0000000000000000 ffff88013f803d40 ffff88013f803d28 ffffffff8109fe2a
[113188.052004]  ffff88013f803d58 ffff88013a15c000 ffff880005f44000 ffff880005f441a0
[113188.052008] Call Trace:
[113188.052010]  <IRQ>  [<ffffffff8176baff>] dump_stack+0x45/0x57
[113188.052018]  [<ffffffff8109fe2a>] warn_slowpath_common+0x8a/0xc0
[113188.052022]  [<ffffffff8109feb5>] warn_slowpath_fmt+0x55/0x70
[113188.052052]  [<ffffffffa0170801>] intel_check_page_flip+0xd1/0xe0 [i915]
[113188.052074]  [<ffffffffa013a74e>] gen8_irq_handler+0x39e/0x4a0 [i915]
[113188.052078]  [<ffffffff810f3e0e>] handle_irq_event_percpu+0x3e/0x1a0
[113188.052081]  [<ffffffff810f3fb1>] handle_irq_event+0x41/0x70
[113188.052082]  [<ffffffff810f726f>] handle_edge_irq+0x7f/0x120
[113188.052085]  [<ffffffff810f348b>] generic_handle_irq+0x2b/0x40
[113188.052089]  [<ffffffff8147b3ca>] evtchn_fifo_handle_events+0x17a/0x190
[113188.052091]  [<ffffffff8147801f>] __xen_evtchn_do_upcall+0x4f/0x90
[113188.052094]  [<ffffffff81479f64>] xen_evtchn_do_upcall+0x34/0x50
[113188.052096]  [<ffffffff8177571e>] xen_do_hypervisor_callback+0x1e/0x40
[113188.052097]  <EOI>  [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20
[113188.052103]  [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20
[113188.052105]  [<ffffffff8100a2f0>] ? xen_safe_halt+0x10/0x20
[113188.052108]  [<ffffffff81020bee>] ? default_idle+0x1e/0xc0
[113188.052111]  [<ffffffff810217cf>] ? arch_cpu_idle+0xf/0x20
[113188.052114]  [<ffffffff810e4414>] ? cpu_startup_entry+0x324/0x3f0
[113188.052117]  [<ffffffff8175c5fc>] ? rest_init+0x7c/0x80
[113188.052121]  [<ffffffff81d4e13c>] ? start_kernel+0x49e/0x4bf
[113188.052123]  [<ffffffff81d4da8e>] ? set_init_arg+0x55/0x55
[113188.052126]  [<ffffffff81d4d5ee>] ? x86_64_start_reservations+0x2a/0x2c
[113188.052128]  [<ffffffff81d50a38>] ? xen_start_kernel+0x518/0x524
[113188.052129] ---[ end trace 0b395a5bbdc63941 ]---

[marmarek]

Thanks for more data on it, it is already tracked in #1028

[marmarek]

Thanks for more data on it, it is already tracked in #1028