i915 regression in kernel 4.10

[Juergen Gross]

With recent 4.10 kernel the graphics isn't coming up under Xen. First
failure message is:

[   46.656649] i915 0000:00:02.0: swiotlb buffer is full (sz: 1630208 bytes)

Later I see splats like:

[   49.393583] general protection fault: 0000 [#1] SMP
[   49.403800] Modules linked in: bridge stp llc tun arc4 iwldvm
mac80211 uvcvideo snd_hda_codec_realtek snd_hda_codec_hdmi
videobuf2_vmalloc snd_hda_codec_generic videobuf2_memops snd_hda_intel
videobuf2_v4l2 snd_hda_codec videobuf2_core iwlwifi videodev
snd_hda_core e1000e intel_rapl xhci_pci x86_pkg_temp_thermal xhci_hcd
intel_powerclamp coretemp crct10dif_pclmul snd_hwdep joydev crc32_pclmul
crc32c_intel ghash_clmulni_intel mei_me ptp iTCO_wdt aesni_intel snd_pcm
ppdev mei aes_x86_64 iTCO_vendor_support lrw sdhci_pci gf128mul lpc_ich
parport_pc pps_core cfg80211 glue_helper ablk_helper snd_timer parport
mfd_core i2c_i801 snd i2c_smbus dell_laptop i2c_hid hid psmouse
dell_rbtn dell_smbios tpm_tis i2c_designware_platform rfkill soundcore
xenfs tpm_tis_core i2c_designware_core tpm dcdbas xen_privcmd evdev
serio_raw battery ac dell_smm_hwmon thermal dell_smo8800 cryptd pcspkr
dm_mod ext4 crc16 jbd2 mbcache sr_mod cdrom sd_mod ahci libahci ehci_pci
ehci_hcd libata usbcore usb_common sdhci_acpi sdhci i915 video mmc_core
i2c_algo_bit drm_kms_helper drm button xen_acpi_processor xen_pciback
xen_netback xen_blkback xen_gntalloc xen_gntdev xen_evtchn
target_core_mod configfs sg scsi_mod autofs4
[   49.616634] CPU: 2 PID: 1663 Comm: gnome-shell Tainted: G        W
   4.8.0-rc2-pv+ #763
[   49.633989] Hardware name: Dell Inc. Latitude E6440/0159N7, BIOS A07
06/26/2014
[   49.649235] task: ffff8801f44ac140 task.stack: ffff8801f944c000
[   49.661738] RIP: e030:[<ffffffffa01f5236>]  [<ffffffffa01f5236>]
gen6_ppgtt_insert_entries+0xd6/0x1f0 [i915]
[   49.682062] RSP: e02b:ffff8801f944faa0  EFLAGS: 00010202
[   49.693355] RAX: 672f726574697254 RBX: ffff8801f46beda0 RCX:
0000000000000000
[   49.708282] RDX: 672f726574697257 RSI: 0000000000000001 RDI:
0000000000000640
[   49.723232] RBP: 0000000003020140 R08: 0000000000000000 R09:
ffff8801f46e2000
[   49.738182] R10: ffff8801f944fc00 R11: 0000000000000007 R12:
0000000000001031
[   49.753110] R13: ffff8801f46e2000 R14: ffff8801f46be000 R15:
0000000000000369
[   49.768039] FS:  00007f0e354e5a80(0000) GS:ffff8801ff900000(0000)
knlGS:ffff8801ff900000
[   49.784879] CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
[   49.797033] CR2: 0000000005636ff0 CR3: 00000001e9c8c000 CR4:
0000000000042660
[   49.811972] Stack:
[   49.816681]  727365642f61632f 0000000100000031 0000000100000000
ffff8801f44ac140
[   49.832131]  ffff8801f45f7a00 0000000000000080 0000000000000001
0000000000000000
[   49.847584]  ffff8801f944fcde ffff8801f45f7a00 ffffffffa01f7333
00000000eb9bbc88
[   49.863045] Call Trace:
[   49.868652]  [<ffffffffa01f7333>] ? aliasing_gtt_bind_vma+0x83/0xd0
[i915]
[   49.883111]  [<ffffffffa01f9e69>] ? i915_vma_bind+0x79/0x110 [i915]
[   49.896345]  [<ffffffffa01fd9cf>] ? __i915_vma_do_pin+0x2ff/0x4c0 [i915]
[   49.910477]  [<ffffffff812d50c9>] ? __radix_tree_insert+0x29/0xc0
[   49.923368]  [<ffffffff811a2e04>] ? kmem_cache_alloc+0x1c4/0x1e0
[   49.936159]  [<ffffffffa01ef701>] ?
i915_gem_execbuffer_reserve_vma.isra.43+0x131/0x1a0 [i915]
[   49.954117]  [<ffffffffa01efa1a>] ?
i915_gem_execbuffer_reserve.isra.44+0x2aa/0x3a0 [i915]
[   49.971352]  [<ffffffffa01f1349>] ?
i915_gem_do_execbuffer.isra.49+0x6a9/0x1690 [i915]
[   49.987889]  [<ffffffff811514a3>] ? __alloc_pages_nodemask+0x133/0xc40
[   50.001677]  [<ffffffffa01f2726>] ? i915_gem_execbuffer2+0xd6/0x240
[i915]
[   50.016131]  [<ffffffffa0107781>] ? drm_ioctl+0x191/0x3f0 [drm]
[   50.028675]  [<ffffffffa01f2650>] ? i915_gem_execbuffer+0x320/0x320
[i915]
[   50.043123]  [<ffffffff8117c6cc>] ? handle_mm_fault+0x3ac/0x12e0
[   50.055839]  [<ffffffff811d693a>] ? do_vfs_ioctl+0x8a/0x5b0
[   50.067677]  [<ffffffff811d6ecf>] ? SyS_ioctl+0x6f/0x80
[   50.078815]  [<ffffffff81581b36>] ? entry_SYSCALL_64_fastpath+0x1e/0xa8
[   50.092725] Code: 00 10 00 00 44 3b 64 24 08 72 ae f6 45 00 02 75 66
48 8b 55 20 48 8d 45 20 f6 c2 01 0f 85 f8 00 00 00 48 85 c0 0f 84 fb 00
00 00 <44> 8b 60 08 8b 48 0c 48 89 c5 48 8b 70 10 44 01 e1 44 89 e7 48
[   50.131694] RIP  [<ffffffffa01f5236>]
gen6_ppgtt_insert_entries+0xd6/0x1f0 [i915]
[   50.147396]  RSP <ffff8801f944faa0>
[   50.158793] ---[ end trace 6fc5bf1c09423b3f ]---

I have bisected the commits and found the bug to be introduced in
commit 871dfbd67d4ecbcc83fc9e80a310ca9bf3c44c40 ("drm/i915: Allow
compaction upto SWIOTLB max segment size").

To be able to test this commit with Xen you'll need the attached patch
in order to enable the system to boot or you have to disable loading
of microcode.


Juergen
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