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

[Stefan Weil]

Am 10.09.2012 08:19, schrieb 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

QEMU :-)

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) */

Hi Clemens,

indeed, it looks like CPUID_DE fixes that BSOD with "STOP 0x0000005D ...".
In my test scenario Windows now reboots instead of showing the BSOD.

This commit added the TCG feature bit trimming which broke Windows:

commit 551a2dec8fa55006a68393b9d6fb63577d2b3f1c
Autor:    Andre Przywara <address@hidden>  Do Mär 11 14:39:03 2010
Eintragender:    Aurelien Jarno <address@hidden>  Sa Mär 13 16:50:54 2010

x86/cpuid: add TCG feature bit trimming

In KVM we trim the user provided CPUID bits to match the host CPU's
one. Introduce a similar feature to QEMU/TCG. Create a mask of TCG's
capabilities and apply it to the user bits.
This allows to let the CPU models reflect their native archetypes.

Signed-off-by: Andre Przywara <address@hidden>
Signed-off-by: Aurelien Jarno <address@hidden>

Andre, why don't we set the requested feature bits - no matter what TCG provides?

Regards,

Stefan