boot: 0.981
other: 0.977
semantic: 0.976
instruction: 0.974
device: 0.969
assembly: 0.969
graphic: 0.967
socket: 0.957
KVM: 0.952
vnc: 0.943
mistranslation: 0.938
network: 0.910

Enabling KVM with recent QEMU builds from GIT hang at boot on Ubuntu Precise AMD64 kernel 3.8.0

When I compile QEMU from GIT and run it with './x86_64-softmmu/qemu-system-x86_64 -enable-kvm' it just hangs, the QEMU screen stays black. (Everything else in the GTK UI is responsive though, I can use the QEMU console as well.)
I'm running Ubuntu Precise with kernel 3.8.0-27-generic on an Intel Core2 Duo P9500.

With bisecting, I found this commit caused the problem:

235e8982ad393e5611cb892df54881c872eea9e1 is the first bad commit
commit 235e8982ad393e5611cb892df54881c872eea9e1
Author: Jordan Justen <email address hidden>
Date:   Wed May 29 01:27:26 2013 -0700

    kvm: support using KVM_MEM_READONLY flag for regions

    For readonly memory regions and rom devices in romd_mode,
    we make use of the KVM_MEM_READONLY. A slot that uses
    KVM_MEM_READONLY can be read from and code can execute from the
    region, but writes will exit to qemu.

    For rom devices with !romd_mode, we force the slot to be
    removed so reads or writes to the region will exit to qemu.
    (Note that a memory region in this state is not executable
    within kvm.)

    v7:
     * Update for readable => romd_mode rename (5f9a5ea1)

    Signed-off-by: Jordan Justen <email address hidden>
    Reviewed-by: Xiao Guangrong <email address hidden> (v4)
    Reviewed-by: Paolo Bonzini <email address hidden> (v5)
    Message-id: <email address hidden>
    Signed-off-by: Anthony Liguori <email address hidden>

:100644 100644 327ae12f08b9dddc796d753d8adfb1f70c78b2c1 8e7bbf8698f6bcaa5ae945ef86e7b51effde06fe M      kvm-all.c

We have discussed this issue in this mail:
http://<email address hidden>/msg174932.html (VM can
not boot after commit 235e898)

You can upgrade your kernel to 3.9.x to work around.


On Thu, Aug 15, 2013 at 3:23 AM, Julius Schwartzenberg <
<email address hidden>> wrote:

> Public bug reported:
>
> When I compile QEMU from GIT and run it with
> './x86_64-softmmu/qemu-system-x86_64 -enable-kvm' it just hangs, the QEMU
> screen stays black. (Everything else in the GTK UI is responsive though, I
> can use the QEMU console as well.)
> I'm running Ubuntu Precise with kernel 3.8.0-27-generic on an Intel Core2
> Duo P9500.
>
> With bisecting, I found this commit caused the problem:
>
> 235e8982ad393e5611cb892df54881c872eea9e1 is the first bad commit
> commit 235e8982ad393e5611cb892df54881c872eea9e1
> Author: Jordan Justen <email address hidden>
> Date:   Wed May 29 01:27:26 2013 -0700
>
>     kvm: support using KVM_MEM_READONLY flag for regions
>
>     For readonly memory regions and rom devices in romd_mode,
>     we make use of the KVM_MEM_READONLY. A slot that uses
>     KVM_MEM_READONLY can be read from and code can execute from the
>     region, but writes will exit to qemu.
>
>     For rom devices with !romd_mode, we force the slot to be
>     removed so reads or writes to the region will exit to qemu.
>     (Note that a memory region in this state is not executable
>     within kvm.)
>
>     v7:
>      * Update for readable => romd_mode rename (5f9a5ea1)
>
>     Signed-off-by: Jordan Justen <email address hidden>
>     Reviewed-by: Xiao Guangrong <email address hidden> (v4)
>     Reviewed-by: Paolo Bonzini <email address hidden> (v5)
>     Message-id:
> <email address hidden>
>     Signed-off-by: Anthony Liguori <email address hidden>
>
> :100644 100644 327ae12f08b9dddc796d753d8adfb1f70c78b2c1
> 8e7bbf8698f6bcaa5ae945ef86e7b51effde06fe M      kvm-all.c
>
> ** Affects: qemu
>      Importance: Undecided
>          Status: New
>
> --
> You received this bug notification because you are a member of qemu-
> devel-ml, which is subscribed to QEMU.
> https://bugs.launchpad.net/bugs/1212402
>
> Title:
>   Enabling KVM with recent QEMU builds from GIT hang at boot on Ubuntu
>   Precise AMD64 kernel 3.8.0
>
> Status in QEMU:
>   New
>
> Bug description:
>   When I compile QEMU from GIT and run it with
> './x86_64-softmmu/qemu-system-x86_64 -enable-kvm' it just hangs, the QEMU
> screen stays black. (Everything else in the GTK UI is responsive though, I
> can use the QEMU console as well.)
>   I'm running Ubuntu Precise with kernel 3.8.0-27-generic on an Intel
> Core2 Duo P9500.
>
>   With bisecting, I found this commit caused the problem:
>
>   235e8982ad393e5611cb892df54881c872eea9e1 is the first bad commit
>   commit 235e8982ad393e5611cb892df54881c872eea9e1
>   Author: Jordan Justen <email address hidden>
>   Date:   Wed May 29 01:27:26 2013 -0700
>
>       kvm: support using KVM_MEM_READONLY flag for regions
>
>       For readonly memory regions and rom devices in romd_mode,
>       we make use of the KVM_MEM_READONLY. A slot that uses
>       KVM_MEM_READONLY can be read from and code can execute from the
>       region, but writes will exit to qemu.
>
>       For rom devices with !romd_mode, we force the slot to be
>       removed so reads or writes to the region will exit to qemu.
>       (Note that a memory region in this state is not executable
>       within kvm.)
>
>       v7:
>        * Update for readable => romd_mode rename (5f9a5ea1)
>
>       Signed-off-by: Jordan Justen <email address hidden>
>       Reviewed-by: Xiao Guangrong <email address hidden> (v4)
>       Reviewed-by: Paolo Bonzini <email address hidden> (v5)
>       Message-id:
> <email address hidden>
>       Signed-off-by: Anthony Liguori <email address hidden>
>
>   :100644 100644 327ae12f08b9dddc796d753d8adfb1f70c78b2c1
>   8e7bbf8698f6bcaa5ae945ef86e7b51effde06fe M      kvm-all.c
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/qemu/+bug/1212402/+subscriptions
>
>


-- 
Best Regards,

Dunrong Huang

Homepage: http://mathslinux.org


It seems reverting this exact commit also works around the problem. I have attached a patch against current head.

According to comment #1, this has been fixed with kernel 3.9, so setting the status to "Fix released" now.