Re: [Bug #13116] Can't boot with nosmp

[Avi Kivity]

Dan Williams wrote:
> On Mon, Jun 8, 2009 at 5:04 PM, Stephen Hemminger<shemminger@xxxxxxxxxx> wrote:
>   
> > I did some more debugging, and the problem appears to be that
> > booting with nosmp still leaves all the CPU's present in the cpu
> > possible mask. So code like dma engine (or loopback device), that
> > use alloc_percpu get broken.
> >
> > Not sure why all the cpu's are still showing up in the possible mask.
> > Rusty? do you have an answer.
> >     
>
> Would this recent commit also fix this issue?
>
> commit a4c0364be3f43d3e17fe19270f8b3d64881606e6
> Author: Avi Kivity <avi@xxxxxxxxxx>
> Date:   Sat Jun 6 12:34:39 2009 +0300
>
>     KVM: Explicity initialize cpus_hardware_enabled
>
>     Under CONFIG_MAXSMP, cpus_hardware_enabled is allocated from the heap and
>     not statically initialized.  This causes a crash on reboot when kvm thinks
>     vmx is enabled on random nonexistent cpus and accesses nonexistent percpu
>     lists.
>
>     Fix by explicitly clearing the variable.
>
>     Cc: stable@xxxxxxxxxx
>     Reported-and-tested-by: Yinghai Lu <yinghai@xxxxxxxxxx>
>     Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
>   

This only affects reboots.  But yes, the cpumask code has bugs.  Does 
the .config involved select MAXSMP?

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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