[Qemu-devel] KQEMU bus errors

[Qemu-devel] KQEMU bus errors

[Darryl Dixon]

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Hi Fabrice,

    WinXP SP2 guest generates random bus errors during the login process
with kqemu module:
[dixond@localhost machine]$ sudo /opt/src/machine/winxp_boot.sh
Connected to host network interface: tun0
QEMU 0.6.2 monitor - type 'help' for more information
(qemu) /opt/src/machine/winxp_boot.sh: line 2:  6633 Bus error
qemu -hda winxp_hda.img -boot c -enable-audio -nics 1 -m 368 -n qemu-
ifup -monitor stdio -localtime

     Let me know if there is anything I can do to help debug this.

Cheers,
-- 
Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net>

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Re: [Qemu-devel] KQEMU bus errors

[Julian Chesterfield]

I have the same experience running WinXP, SP2 image over latest CVS build 
of KQemu, however testing with both kernel support enabled and disabled 
seems to produce the same error regardless. Anyone else experiencing this with 
XP images?

- Julian



Darryl Dixon wrote:

> Hi Fabrice,
>
>     WinXP SP2 guest generates random bus errors during the login 
> process with kqemu module:
> [dixond@localhost machine]$ sudo /opt/src/machine/winxp_boot.sh
> Connected to host network interface: tun0
> QEMU 0.6.2 monitor - type 'help' for more information
> (qemu) */opt/src/machine/winxp_boot.sh: line 2:  6633 Bus 
> error               qemu -hda winxp_hda.img -boot c -enable-audio 
> -nics 1 -m 368 -n qemu-ifup -monitor stdio -localtime*
>
>      Let me know if there is anything I can do to help debug this.
>
> Cheers,
> -- 
> Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net 
> <mailto:esrever_otua@pythonhacker.is-a-geek.net>>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Qemu-devel mailing list
>Qemu-devel@nongnu.org
>http://lists.nongnu.org/mailman/listinfo/qemu-devel
>  
>

Re: [Qemu-devel] KQEMU bus errors

[Hetz Ben Hamo]

Yes, found the reason...

Test with different ram size - you'll be surprised...

Thanks,
Hetz

On Sun, 13 Feb 2005 01:49:26 +0000, Julian Chesterfield
<julian@thechesterfields.org> wrote:
> I have the same experience running WinXP, SP2 image over latest CVS build
> of KQemu, however testing with both kernel support enabled and disabled
> seems to produce the same error regardless. Anyone else experiencing this with
> XP images?
> 
> - Julian
> 
> 
> Darryl Dixon wrote:
> 
> > Hi Fabrice,
> >
> >     WinXP SP2 guest generates random bus errors during the login
> > process with kqemu module:
> > [dixond@localhost machine]$ sudo /opt/src/machine/winxp_boot.sh
> > Connected to host network interface: tun0
> > QEMU 0.6.2 monitor - type 'help' for more information
> > (qemu) */opt/src/machine/winxp_boot.sh: line 2:  6633 Bus
> > error               qemu -hda winxp_hda.img -boot c -enable-audio
> > -nics 1 -m 368 -n qemu-ifup -monitor stdio -localtime*
> >
> >      Let me know if there is anything I can do to help debug this.
> >
> > Cheers,
> > --
> > Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net
> > <mailto:esrever_otua@pythonhacker.is-a-geek.net>>
> >
> >------------------------------------------------------------------------
> >
> >_______________________________________________
> >Qemu-devel mailing list
> >Qemu-devel@nongnu.org
> >http://lists.nongnu.org/mailman/listinfo/qemu-devel
> >
> >
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

Re: [Qemu-devel] KQEMU bus errors

[Brad Campbell]

Hetz Ben Hamo wrote:
> Yes, found the reason...
> 
> Test with different ram size - you'll be surprised...
> 
I second this one.
I found I had to make sure my tmpfs "partition" was larger than my requested ram size. Problem went 
away.

Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: [Qemu-devel] KQEMU bus errors

[Darryl Dixon]

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Hi,

    I'm not convinced that this is actually the case.  I have tested
this on several machines now with several guest OSes and get the same
result on all of them (which all previously worked).  With the snapshot
from 2005-02-09 all works correctly.  With CVS from 2005-02-11 onwards I
get the error ('Bus error' on host for WinXP guest and 'Protection
Fault' inside guest for Win98 guest).  I think that perhaps with smaller
guest RAM size you are simply hiding the bug.  On one machine at least I
have 756MB physical RAM and 3GB swap allocated and get the same problem.
Most of the references that I can find for a Linux 'Bus error' talk
about unaligned memory accesses.  I did a diff of the 2005-02-09 tree
and the 2005-02-11 tree and noted that most of the *changes* (rather
than additions and new things) were relating to the way that memory is
handled and marked inside qemu.  I think that there is a chance that one
of these has introduced the problem.

Regards,
D

On Sun, 2005-02-13 at 09:14 +0400, Brad Campbell wrote:

> Hetz Ben Hamo wrote:
> > Yes, found the reason...
> > 
> > Test with different ram size - you'll be surprised...
> > 
> I second this one.
> I found I had to make sure my tmpfs "partition" was larger than my requested ram size. Problem went 
> away.
> 
> Brad

-- 
Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net>

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Re: [Qemu-devel] KQEMU bus errors

[Jonas Maebe]

On 13 feb 2005, at 10:42, Darryl Dixon wrote:

> Most of the references that I can find for a Linux 'Bus error' talk 
> about unaligned memory accesses.

Indeed. The only way I know of to get a bus error under Linux/x86 from 
a user space program, is to turn on the alignment check flag in the 
eflags register, followed by an unaligned memory access.

Usually, this is the result from a corrupted stack, causing an invalid 
value to be restored to the eflags register (which coincidentally has 
the bit corresponding to the alignment check flag set to 1).


Jonas

Re: [Qemu-devel] KQEMU bus errors

[Julian Seward]

On Sunday 13 February 2005 11:13, Jonas Maebe wrote:
> On 13 feb 2005, at 10:42, Darryl Dixon wrote:
> > Most of the references that I can find for a Linux 'Bus error' talk
> > about unaligned memory accesses.
>
> Indeed. The only way I know of to get a bus error under Linux/x86 from
> a user space program, is to turn on the alignment check flag in the
> eflags register, followed by an unaligned memory access.

I have a very vague and possibly wrong memory that the another way
to get a bus error is to mmap a file into an area which is too big
for the file, then read/write the area beyond the end of the file.
Or perhaps that was on Solaris.  In any case, it might be worth
checking this isn't somehow related to mmap or use of mmap.

J

Re: [Qemu-devel] KQEMU bus errors

[Grzegorz Kulewski]

On Sun, 13 Feb 2005, Julian Seward wrote:

> On Sunday 13 February 2005 11:13, Jonas Maebe wrote:
>> On 13 feb 2005, at 10:42, Darryl Dixon wrote:
>>> Most of the references that I can find for a Linux 'Bus error' talk
>>> about unaligned memory accesses.
>>
>> Indeed. The only way I know of to get a bus error under Linux/x86 from
>> a user space program, is to turn on the alignment check flag in the
>> eflags register, followed by an unaligned memory access.
>
> I have a very vague and possibly wrong memory that the another way
> to get a bus error is to mmap a file into an area which is too big
> for the file, then read/write the area beyond the end of the file.
> Or perhaps that was on Solaris.  In any case, it might be worth
> checking this isn't somehow related to mmap or use of mmap.

>From man mmap(2):

"SIGBUS Attempted access to a portion of the buffer that does not 
correspond to the file (for example,
               beyond  the end of the file, including the case where 
another process has truncated the file)."

So this is very probable that the errors are caused by too small 
limit of tmpfs mounted on /dev/shm.


Grzegorz Kulewski

[Qemu-devel] Bus errors and /dev/shm -- was: KQEMU bus errors

[Darryl Dixon]

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I'm not quite clear on why /dev/shm should affect the 2005-02-11 version
and not the 2005-02-09 version of the code, but I took you at your word
and tried first with qemu guest mem == size of /dev/shm, and once again
received 'Bus error'.  I then set qemu guest mem == 3/4 of /dev/shm and
it seems to be working OK.

So, can anyone explain why the apparent regression, and why /dev/shm is
used at all?  I would be happier if I understood :)

Incidentally, the 'Protection Error' received by Win9x guest appears to
be orthogonal to this problem and isn't fixed by the above like WinXP
is.

Cheers,
D


On Sun, 2005-02-13 at 15:51 +0100, Grzegorz Kulewski wrote:

> On Sun, 13 Feb 2005, Julian Seward wrote:
> 
> > On Sunday 13 February 2005 11:13, Jonas Maebe wrote:
> >> On 13 feb 2005, at 10:42, Darryl Dixon wrote:
> >>> Most of the references that I can find for a Linux 'Bus error' talk
> >>> about unaligned memory accesses.
> >>
> >> Indeed. The only way I know of to get a bus error under Linux/x86 from
> >> a user space program, is to turn on the alignment check flag in the
> >> eflags register, followed by an unaligned memory access.
> >
> > I have a very vague and possibly wrong memory that the another way
> > to get a bus error is to mmap a file into an area which is too big
> > for the file, then read/write the area beyond the end of the file.
> > Or perhaps that was on Solaris.  In any case, it might be worth
> > checking this isn't somehow related to mmap or use of mmap.
> 
> >From man mmap(2):
> 
> "SIGBUS Attempted access to a portion of the buffer that does not 
> correspond to the file (for example,
>                beyond  the end of the file, including the case where 
> another process has truncated the file)."
> 
> So this is very probable that the errors are caused by too small 
> limit of tmpfs mounted on /dev/shm.
> 
> 
> Grzegorz Kulewski
> 
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel

-- 
Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net>

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Re: [Qemu-devel] Bus errors and /dev/shm -- was: KQEMU bus errors

[Filip Navara]

Darryl Dixon wrote:

> So, can anyone explain why the apparent regression, and why /dev/shm 
> is used at all?  I would be happier if I understood :)

The memory allocation of KQEMU-enabled QEMU binaries has changed. A 
temporary file representing the guest virtual memory is created in the 
QEMU_TMPDIR directory (defaults to "/dev/shm" if not set) and is mmaped 
in the QEMU process.

- Filip

Re: [Qemu-devel] KQEMU bus errors

[Phil Krylov]

Hi,

Here I experience just the opposite: with the 2005-02-12 version of
QEMU + KQEMU, it is the first time I have successfully installed WinXP
guest (Professional Corporate Edition, no Service Pack), and it works
flawlessly.

-- Ph.

Re: [Qemu-devel] KQEMU bus errors

[Darryl Dixon]

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Yes, after further testing I too realised that it was both with and
without kqemu support compiled in on latest CVS.

Cheers,
D


On Sun, 2005-02-13 at 01:49 +0000, Julian Chesterfield wrote:

> I have the same experience running WinXP, SP2 image over latest CVS build 
> of KQemu, however testing with both kernel support enabled and disabled 
> seems to produce the same error regardless. Anyone else experiencing this with 
> XP images?
> 
> - Julian
> 
> 
> 
> Darryl Dixon wrote:
> 
> > Hi Fabrice,
> >
> >     WinXP SP2 guest generates random bus errors during the login 
> > process with kqemu module:
> > [dixond@localhost machine]$ sudo /opt/src/machine/winxp_boot.sh
> > Connected to host network interface: tun0
> > QEMU 0.6.2 monitor - type 'help' for more information
> > (qemu) */opt/src/machine/winxp_boot.sh: line 2:  6633 Bus 
> > error               qemu -hda winxp_hda.img -boot c -enable-audio 
> > -nics 1 -m 368 -n qemu-ifup -monitor stdio -localtime*
> >
> >      Let me know if there is anything I can do to help debug this.
> >
> > Cheers,
> > -- 
> > Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net 
> > <mailto:esrever_otua@pythonhacker.is-a-geek.net>>
> >
> >------------------------------------------------------------------------
> >
> >_______________________________________________
> >Qemu-devel mailing list
> >Qemu-devel@nongnu.org
> >http://lists.nongnu.org/mailman/listinfo/qemu-devel
> >  
> >
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel

-- 
Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net>

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Re: [Qemu-devel] KQEMU bus errors

[Grzegorz Kulewski]

Hi,

Maybe try:

su -
ulimit -c 1024

<make it crash here - it should dump core>

gdb <path-to-qemu> core
bt
quit

and send the output.

Remember to compile qemu with -g flag if it is not compiled with it by 
default.

I do not know if it will bring some interesting info but I can not try it 
myself at the moment because I am too busy.


Grzegorz Kulewski


On Sun, 13 Feb 2005, Julian Chesterfield wrote:

> I have the same experience running WinXP, SP2 image over latest CVS build of 
> KQemu, however testing with both kernel support enabled and disabled seems to 
> produce the same error regardless. Anyone else experiencing this with XP 
> images?
>
> - Julian
>
>
>
> Darryl Dixon wrote:
>
>> Hi Fabrice,
>> 
>>    WinXP SP2 guest generates random bus errors during the login process 
>> with kqemu module:
>> [dixond@localhost machine]$ sudo /opt/src/machine/winxp_boot.sh
>> Connected to host network interface: tun0
>> QEMU 0.6.2 monitor - type 'help' for more information
>> (qemu) */opt/src/machine/winxp_boot.sh: line 2:  6633 Bus error 
>> qemu -hda winxp_hda.img -boot c -enable-audio -nics 1 -m 368 -n qemu-ifup 
>> -monitor stdio -localtime*
>> 
>> Let me know if there is anything I can do to help debug this.
>> 
>> Cheers,
>> -- 
>> Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net 
>> <mailto:esrever_otua@pythonhacker.is-a-geek.net>>
>> 
>> ------------------------------------------------------------------------
>> 
>> _______________________________________________
>> Qemu-devel mailing list
>> Qemu-devel@nongnu.org
>> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>> 
>> 
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

[Qemu-devel] Re: KQEMU bus errors

[bri3d]

> 
> I have the same experience running WinXP, SP2 image over latest CVS build 
> of KQemu, however testing with both kernel support enabled and disabled 
> seems to produce the same error regardless. Anyone else experiencing this with 
> XP images?
> 
> - Julian

Yes.  Just for kicks I tried the XP SP2 installer CD too(XP SP1 CD slipstreamed
to SP2+February 2005 patches, ISO not real CD).  It crashes at the "formatting
disk" step with all disk image types until I make ram less then /dev/shm.  Then
it formats OK.

Re: [Qemu-devel] Re: KQEMU bus errors

[Hetz Ben Hamo]

> Yes.  Just for kicks I tried the XP SP2 installer CD too(XP SP1 CD slipstreamed
> to SP2+February 2005 patches, ISO not real CD).  It crashes at the "formatting
> disk" step with all disk image types until I make ram less then /dev/shm.  Then
> it formats OK.

How do I setup the /dev/shm and with what parameters?

Thanks,
Hetz

Re: [Qemu-devel] Re: KQEMU bus errors

[Darryl Dixon]

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The line from your /etc/fstab should be:

none    /dev/shm    tmpfs    defaults    0 0


Cheers,
D


On Tue, 2005-02-22 at 01:04 +0200, Hetz Ben Hamo wrote:

>> Yes.  Just for kicks I tried the XP SP2 installer CD too(XP SP1 CD slipstreamed
>> to SP2+February 2005 patches, ISO not real CD).  It crashes at the "formatting
>> disk" step with all disk image types until I make ram less then /dev/shm.  Then
>> it formats OK.
>
>How do I setup the /dev/shm and with what parameters?
>
>Thanks,
>Hetz
>
>
>_______________________________________________
>Qemu-devel mailing list
>Qemu-devel@nongnu.org
>http://lists.nongnu.org/mailman/listinfo/qemu-devel

-- 
Darryl Dixon <esrever_otua@pythonhacker.is-a-geek.net>

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