Re: system freeze with kernel 3.2-rc7

[Keith Packard <keithp@keithp.com>]

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On Mon, 26 Dec 2011 03:43:22 +0100, Kai Krakow <hurikhan77@gmail.com> wrote:
> Keith Packard <keithp@keithp.com> schrieb:
> 
> > On Mon, 26 Dec 2011 01:43:37 +0100, Kai Krakow <hurikhan77@gmail.com>
> > wrote:
> > 
> >> I didn't have such issues with early 3.2 rcs (afair), and not with 3.1
> >> kernels. After some digging through google I've found you enabled RC6 in
> >> 3.2. I disabled it now, and my system runs wonderfully.
> > 
> > Argh. Can you try building a kernel with VT-d support? I assume you
> > can't turn VT-d off in the BIOS as it's UEFI?
> 
> kakra@jupiter ~ $ zgrep -i iommu /proc/config.gz 
> CONFIG_GART_IOMMU=y
> # CONFIG_CALGARY_IOMMU is not set
> CONFIG_IOMMU_HELPER=y
> CONFIG_IOMMU_API=y
> CONFIG_IOMMU_SUPPORT=y
> # CONFIG_AMD_IOMMU is not set
> CONFIG_INTEL_IOMMU=y
> CONFIG_INTEL_IOMMU_DEFAULT_ON=y
> CONFIG_INTEL_IOMMU_FLOPPY_WA=y
> # CONFIG_IOMMU_DEBUG is not set
> # CONFIG_IOMMU_STRESS is not set
> 
> So kernel vt-d support is on. Not sure what to look for in dmesg thou... I 
> didn't look into the BIOS settings yet, but usually if there is such an 
> option I turn it on because I use virtual machines.

You almost certainly don't need IOMMU/VT-d support though; that
virtualizes devices for DMA by the guest OS, which generally no-one
does.

The BIOS manual for the Z68 board mentions two configuration options,

CPU Configuration:

    Intel Virtualization Technology
        When this option is set to [Enabled], a VMM (Virtual Machine
        Architecture) can utilize the additional hardware capabilities
        provided by Vanderpool Technology. This option will be hidden if
        the installed CPU does not support Intel Virtualization
        Technology.

North Bridge Configuration:

    VT-d
        Use this to enable or disable Intel® VT-d technology (Intel®
        Virtualization Technology for Directed I/O). The default value
        of this feature is [Disabled].

I'd love to see tests with these in the three possible combinations:

        VT enabled, VT-d enabled
        VT enabled, VT-d disabled
        VT disabled, VT-d disabled

Meanwhile, I'll get a patch ready for 3.2 which disables RC6 again.

-- 
keith.packard@intel.com

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