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

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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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