Hi Mihai, You have a gen4.5 chipset which is known to be utterly broken for IOMMU+intel gpu. Looks like a few distros started enabling IOMMU by default (fc18 has similar issues) and we've never added the proper quirks. See https://bugzilla.kernel.org/show_bug.cgi?id=51921 for a proposed patch to fix this (i.e. automatically set intel_iommu=igfx_off for affected platfroms). Testing highly welcome. Cheers, Daniel On Sat, Jan 19, 2013 at 12:48 AM, Mihai Moldovan <ionic at ionic.de> wrote: > Hi Daniel, David and everyone else, > > I'm experiencing system freezes on a box using the vanilla 3.7.2 (actually down > to 3.2 or something) kernel with a custom configuration. > > There are two problems: > > [*] related to i915 with modeset enabled; upon loading the kernel module with > modeset=1, the box will instantly freeze. > [*] seemingly unrelated to i915; the box will randomly freeze without any > clear indication of why and moreover no apparent trigger. > > After months, nay, years of being "locked" into 3.0.2 for the random freezes and > i915 problems, I started playing with the kernel again and out of sheer > desperation installed the current debian testing kernel, based on 3.2.35. > > From what I could see, it worked fine... no more crashes, neither when loading > i915, nor randomly after some time (well, at least not for a day.) > > This time out of frustration, I ripped the config file used by debian to build > the kernel out of its deb package and rebuilt my (almost[1]) vanilla 3.7.2 > kernel with this configuration exactly, updated via the oldconfig target and > changed to include AHCI, RAID and SCSI drivers statically, so that I wouldn't > need some initramfs to boot my system ... and ... with this config, I am not > experiencing any i915 problems nor system freezes?! > > I then tried to spot any "obvious" differences between the two config files and > to "approximate" my config file to the debian config. > > Comparing the dmesg output from 3.7.2 built with the slightly modified debian > config to my 3.7.2 built with my config, I came across IOMMU entries which > differed. My kernel config enables Intel IOMMU by default, while the debian > config doesn't. > > Looking up IOMMU stuff in Documentation/, I found out that IOMMU *may* have bugs > with the internal graphics card and there is an option called > intel_iommu=igfx_off to disable IOMMU remapping for the integrated graphics card... > > I tried booting "my" kernel with intel_iommu=igfx_off and lo and behold, no more > crashes when loading i915 with modeset enabled! Yay... but anyway, that's > definitely a kernel bug. > > Next, regarding the random freezes... so did the kernel booted with > intel_iommu=igfx_off. It seems the random freeze issue is kind of decoupled of > the graphics issue. > > Testing further, I rebooted using iommu=off and intel_iommu=off. So far, I had > no random crashes, but the system uptime of XXXXREPLACEMEXXXX minutes is too > small to draw conclusions yet. > > Anyway, booting with both options made my USB ports unusable. Also, my PCIe and > PCI WiFi cards stopped working. Seems like the kernel can't enumerate those > devices due to... guess what, DMA remapping errors! > > Note that the debian-config kernel with CONFIG_INTEL_IOMMU=y and > CONFIG_INTEL_IOMMU_DEFAULT_ON=n did not produce such errors. Both my USB and > WiFi cards have been working. > > Any idea why is that? > > As I'm not sure who to CC exactly, I'm adding both the i915 and Intel IOMMU > maintainers Daniel and David. > > I have included several files: > > [*] the "debianish" config file > [*] my current config file (IOMMU still on by default) > [*] dmesg for the kernel built with the "debianish" config file > [*] dmesg for the kernel built with "my" config file, no IOMMU options passed > [*] dmesg for the kernel built with "my" config file, intel_iommu=igfx_off passed > [*] dmesg for the kernel built with "my" config file, iommu=off and > intel_iommu=off passed > > Hope we can squash those bugs! > > Best regards, > > > > Mihai > > > > > [1] only one "external" patch applied to ath9k, totally unrelated to the rest of > the system, just changing regulatory stuff. > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
