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

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Message-ID: <e9c3a7c20906091020m19abf3b5wbbb7f5364b2d4905@mail.gmail.com>
Date:	Tue, 9 Jun 2009 10:20:36 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	avi@...hat.com
Subject: Re: [Bug #13116] Can't boot with nosmp

On Mon, Jun 8, 2009 at 5:04 PM, Stephen Hemminger<shemminger@...tta.com> 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@...hat.com>
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@...nel.org
    Reported-and-tested-by: Yinghai Lu <yinghai@...nel.org>
    Signed-off-by: Avi Kivity <avi@...hat.com>

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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