[Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Aurelien Jarno]

Avi Kivity a écrit :
> Aurelien Jarno wrote:
>> Avi Kivity a écrit :
>>   
>>> Aurelien Jarno wrote:
>>>     
>>>>>> I also confirm that using -no-acpi fixes the problem. However, I have
>>>>>> seen strange data corruption, even on Intel.
>>>>>>
>>>>>> Basically, booting a recently installed FreeBSD leads to the following
>>>>>> message from the bootloader: "No kernel found". And the next time, I get
>>>>>> from the *BIOS*: "Boot from Hard Disk failed: not a bootable disk".
>>>>>>
>>>>>> Looking at the disk image, the partition table (and maybe more?) has
>>>>>> disappeared. This is with a raw image disk.
>>>>>>

[snip]

>> After a few more tests, I have been able to reproduce it with the
>> current CVS version of QEMU. I conclude this is a QEMU or a BIOS
>> problem, and not a KVM one.
>>
>> Sorry for the noise.
>>   
> 
> Well, it still needs to be fixed.  I think there's a git import of qemu 
> available somewhere, that can be used for bisecting.
> 

Well the IDE code hasn't changed a lot recently, so I checked the CVS
history and easily (first test) found the commit that causes the problem:

Last AIO patch, by Vladimir N. Oleynik.

http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65

-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
   `-    people.debian.org/~aurel32 | www.aurel32.net

[Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Avi Kivity]

Aurelien Jarno wrote:
> Well the IDE code hasn't changed a lot recently, so I checked the CVS
> history and easily (first test) found the commit that causes the problem:
>
> Last AIO patch, by Vladimir N. Oleynik.
>
> http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65
>
>   

Have we learned something about this issue?  Should I revert the patch
from kvm?  Should qemu?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: [Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Fabrice Bellard]

Avi Kivity wrote:
> Aurelien Jarno wrote:
>> Well the IDE code hasn't changed a lot recently, so I checked the CVS
>> history and easily (first test) found the commit that causes the problem:
>>
>> Last AIO patch, by Vladimir N. Oleynik.
>>
>> http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65
>>
>>   
> 
> Have we learned something about this issue?  Should I revert the patch
> from kvm?  Should qemu?

Sure. The conversion from sync to async mode done in this patch is 
incomplete to say the least.

Fabrice.

[Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Aurelien Jarno]

Avi Kivity a écrit :
> Aurelien Jarno wrote:
>> Well the IDE code hasn't changed a lot recently, so I checked the CVS
>> history and easily (first test) found the commit that causes the problem:
>>
>> Last AIO patch, by Vladimir N. Oleynik.
>>
>> http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65
>>
>>   
> 
> Have we learned something about this issue?  Should I revert the patch
> from kvm?  Should qemu?
> 

>From my side, I haven't found time to debug the problem. Instead I am
reverting this patch locally each time I install qemu or kvm.

-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
   `-    people.debian.org/~aurel32 | www.aurel32.net

Re: [Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Avi Kivity]

Fabrice Bellard wrote:
> Avi Kivity wrote:
>> Aurelien Jarno wrote:
>>> Well the IDE code hasn't changed a lot recently, so I checked the CVS
>>> history and easily (first test) found the commit that causes the 
>>> problem:
>>>
>>> Last AIO patch, by Vladimir N. Oleynik.
>>>
>>> http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65 
>>>
>>>
>>>   
>>
>> Have we learned something about this issue?  Should I revert the patch
>> from kvm?  Should qemu?
>
> Sure. The conversion from sync to async mode done in this patch is 
> incomplete to say the least.
>

Is reverting the patch safe, or will it cause new problems?

(I'm not sure what "Sure" above refers to)

-- 
error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Re: [kvm-devel] FreeBSD image hangs during boot

[Fabrice Bellard]

Avi Kivity wrote:
> Fabrice Bellard wrote:
>> Avi Kivity wrote:
>>> Aurelien Jarno wrote:
>>>> Well the IDE code hasn't changed a lot recently, so I checked the CVS
>>>> history and easily (first test) found the commit that causes the 
>>>> problem:
>>>>
>>>> Last AIO patch, by Vladimir N. Oleynik.
>>>>
>>>> http://cvs.savannah.nongnu.org/viewvc/qemu/hw/ide.c?root=qemu&r1=1.64&r2=1.65 
>>>>
>>>>
>>>>   
>>>
>>> Have we learned something about this issue?  Should I revert the patch
>>> from kvm?  Should qemu?
>>
>> Sure. The conversion from sync to async mode done in this patch is 
>> incomplete to say the least.
>>
> 
> Is reverting the patch safe, or will it cause new problems?

The patch must be reverted because it implements incorrectly the AIO 
write case (e.g. nsector is modified before the IO actually takes 
place). The previous code was at least correct if win2k_install_hack was 
not enabled and if one considered than the PIO I/Os were instantaneous.

Regards,

Fabrice.