Re: [Qemu-devel] QEMU (no kvm) Win7 (64bit) boot error

[Clemens Kolbitsch]

On Sat, Sep 8, 2012 at 11:22 AM, Clemens Kolbitsch
<address@hidden> wrote:
> On Fri, Sep 7, 2012 at 9:26 PM, Stefan Weil <address@hidden> wrote:
>> Am 08.09.2012 02:48, schrieb Clemens Kolbitsch:
>>>
>>> Hi guys,
>>>
>>> I need to run Win7 64bit in Qemu without KVM support. I found a few
>>> messages concerning the "unsupported architecture" problem (Windows
>>> shows a BSOD with "STOP 0x0000005D ..." on boot), for example
>>>
>>> http://lists.gnu.org/archive/html/qemu-devel/2011-03/msg01623.html
>>> or
>>> http://permalink.gmane.org/gmane.comp.emulators.qemu/92457
>>>
>>> but I don't think there was ever a solution to the problem - at least
>>> what is proposed does not work (I've tried stable and GIT versions).
>>>
>>> Since I have a decent background of modifying the Qemu internals, I'm
>>> more than happy to contribute to solving this issue, but I'm not sure
>>> if anyone is currently working on it (i.e., I don't want to start at 0
>>> in case someone is about to release a patch).
>>>
>>> Please let me know if there is already a know solution/workaround or
>>> whoever might be working on it, please ping me so we can sync.
>>>
>>> BTW, in case this is necessary, here are the details of what I
>>> need/what is not working:
>>>
>>> Qemu: current git-trunk,
>>>
>>> x86_64-softmmu$ ./qemu-system-x86_64 --version
>>> QEMU emulator version 1.2.50, Copyright (c) 2003-2008 Fabrice Bellard
>>>
>>> host: 64bit, Ubuntu LTS12.04
>>>
>>> guest: 64bit Windows 7, no KVM possible
>>>
>>> Thanks!
>>> -Clemens
>>
>>
>> Hi Clemens,
>>
>> AFAIK, nobody is working on this issue which exists for a long time now.
>> It would be great if you could find a solution to make QEMU without KVM
>> work with Windows guests.
>
> Hi Stefan,
>
> thanks for the info. I'll work on it then - hopefully I can come back
> with a patch soon!
>
>> PS: It's QEMU, not Qemu. I modified the subject in my reply :-)
>
> hehe, old habbit :) I'll try to remember - but why is the ML then
> called "Qemu-devel" ? ;)

After a first night of debugging, I have come up with a simple patch.
I'm still testing and it seems it's not the ultimate solution yet
(there are still bluescreens), but it already gets you much further
while booting (using either the install CD or an actual image).

This diffs against the current stable-1.1. As you can see, one of the
feature bits of the CPUID are removed due to TCG not supporting them
(or the TCG bitmask is just missing them). Since Qemu uses CPUID_DE in
other locations, I'm assuming the bitmask is just wrong.

Can someone confirm that TCG supports CPUID_DE ? If not, I'll need to
work on this, otherwise I'll investigate why Win7 still crashes with a
BSOD.

Thanks!
Clemens


qemu$ git diff
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 388bc5c..f2af36d 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -259,7 +259,8 @@ typedef struct x86_def_t {
           CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC | CPUID_SEP | \
           CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV | CPUID_PAT | \
           CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | \
-          CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS)
+          CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | \
+          CPUID_DE) /* needed by Win7 64bit */
           /* partly implemented:
           CPUID_MTRR, CPUID_MCA, CPUID_CLFLUSH (needed for Win64)
           CPUID_PSE36 (needed for Solaris) */