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

From: Dan Williams
Date: Tue Jun 09 2009 - 13:20:50 EST

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

Fix by explicitly clearing the variable.

Cc: stable@xxxxxxxxxx
Reported-and-tested-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1ecbe23..4293528 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2305,6 +2305,7 @@ int kvm_init(void *opaque, unsigned int vcpu_size,
r = -ENOMEM;
goto out_free_0;
+ cpumask_clear(cpus_hardware_enabled);

r = kvm_arch_hardware_setup();
if (r < 0)
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