[Qemu-devel] IDE TRIM bug on at least PPC target

[Qemu-devel] IDE TRIM bug on at least PPC target

[Michael Tokarev]

As mentioned in LP:1179104 ( https://bugs.launchpad.net/qemu/+bug/1179104 ),
there's a segfault bug in qemu process once guest tries to use some TRIM
command against an IDE device on PPC.  This makes qemu-system-ppc basically
unusable with any modern distribution, since mke2fs now issues TRIM commands
during install by default.  I think it is critical enough bug to warrant
some last-minute hunting/fixing, and it'd be a shame to make a release
of qemu with this bug.

That's more or less a JFYI for now, but I don't really know what other info
is needed, -- I already provided some structures content from a gdb session.

Thanks,

/mjt

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Paolo Bonzini]

Il 18/05/2013 15:30, Michael Tokarev ha scritto:
> As mentioned in LP:1179104 ( https://bugs.launchpad.net/qemu/+bug/1179104 ),
> there's a segfault bug in qemu process once guest tries to use some TRIM
> command against an IDE device on PPC.  This makes qemu-system-ppc basically
> unusable with any modern distribution, since mke2fs now issues TRIM commands
> during install by default.  I think it is critical enough bug to warrant
> some last-minute hunting/fixing, and it'd be a shame to make a release
> of qemu with this bug.
> 
> That's more or less a JFYI for now, but I don't really know what other info
> is needed, -- I already provided some structures content from a gdb session.

Command line and an image (even something generic like "debian wheezy
PPC installation image at this URL") would help.

The workaround is simply to use virtio.  Did you test SCSI as well?

Paolo

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Michael Tokarev]

18.05.2013 17:39, Paolo Bonzini wrote:
> Il 18/05/2013 15:30, Michael Tokarev ha scritto:
>> As mentioned in LP:1179104 ( https://bugs.launchpad.net/qemu/+bug/1179104 ),
[]
>> That's more or less a JFYI for now, but I don't really know what other info
>> is needed, -- I already provided some structures content from a gdb session.
> 
> Command line and an image (even something generic like "debian wheezy
> PPC installation image at this URL") would help.

The bugreport referenced has both, with the only issue is that you have to
actually get in the debian install process to the point where it starts
writing to disk -- it asks many questions before that, but once it tries
to create filesystems it crashes.

> The workaround is simply to use virtio.  Did you test SCSI as well?

Trying that now.

Thanks,

/mjt

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Michael Tokarev]

18.05.2013 17:48, Michael Tokarev wrote:
> 18.05.2013 17:39, Paolo Bonzini wrote:
>> [] Did you test SCSI as well?
> 
> Trying that now.

And I don't really know how to add scsi device to qemu ppc.

 qemu-system-ppc -drive file=foo,if=scsi

creates no scsi device in the guest, at least not one visible
by lspci.  How to use scsi with ppc?

Thanks,

/mjt

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Paolo Bonzini]

Il 18/05/2013 16:39, Michael Tokarev ha scritto:
> 18.05.2013 17:48, Michael Tokarev wrote:
>> 18.05.2013 17:39, Paolo Bonzini wrote:
>>> [] Did you test SCSI as well?
>>
>> Trying that now.
> 
> And I don't really know how to add scsi device to qemu ppc.
> 
>  qemu-system-ppc -drive file=foo,if=scsi
> 
> creates no scsi device in the guest, at least not one visible
> by lspci.  How to use scsi with ppc?

For example:

qemu-system-ppc -drive file=foo,if=none,id=hd -device \
  megasas -device scsi-disk,drive=hd

Paolo

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Michael Tokarev]

18.05.2013 19:53, Paolo Bonzini wrote:
> Il 18/05/2013 16:39, Michael Tokarev ha scritto:
>> And I don't really know how to add scsi device to qemu ppc.
>>
>>  qemu-system-ppc -drive file=foo,if=scsi


> For example:
> 
> qemu-system-ppc -drive file=foo,if=none,id=hd -device \
>   megasas -device scsi-disk,drive=hd

This creates megasas device in the guest, but it does
not work still, at least with the debian wheezy (current)
kernel.  It tries to load megaraid_sas module, and is
getting this:

 scsi3 : LSI SAS based MegaRAID driver
 irq 22: nobody cared (try booting with the "irqpool" option)
 ...
 --- Exception: 501 at __do_softirq+0x6c/0x1dc
     LR = call_do_softirq+0x14/0x24
 ...
 --- Exception: 501 at megasas_fire_cmd_ppc+0x28/0x2c [megaraid_sas]
     LR = megasas_issue_dcmd+0x28/0x38 [megaraid_sas]
 ...
 Disabling IRQ #22
 scsi 3:0:0:0: megasas: RESET cmd=12 retries=0
 megasas: [ 0]waiting for 1 commands to complete
 megasas: [10]waiting for 1 commands to complete
 INFO: task modprobe:4017 blocked for more than 120 seconds.
 ...

and so on.

So I'm afraid megasas isn't exactly useful in this situation.

Thanks,

/mjt

Re: [Qemu-devel] IDE TRIM bug on at least PPC target

[Aurelien Jarno]

On Sat, May 18, 2013 at 05:30:03PM +0400, Michael Tokarev wrote:
> As mentioned in LP:1179104 ( https://bugs.launchpad.net/qemu/+bug/1179104 ),
> there's a segfault bug in qemu process once guest tries to use some TRIM
> command against an IDE device on PPC.  This makes qemu-system-ppc basically
> unusable with any modern distribution, since mke2fs now issues TRIM commands
> during install by default.  I think it is critical enough bug to warrant
> some last-minute hunting/fixing, and it'd be a shame to make a release
> of qemu with this bug.
> 
> That's more or less a JFYI for now, but I don't really know what other info
> is needed, -- I already provided some structures content from a gdb session.
> 

I have just sent a patch to fix this issue. It would be nice if it can
be reviewed shortly, so that it can be included in 1.5.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net