linux-kernel - Re: [PATCH] xen/x86: Initialize per_cpu(xen

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Date:   Mon, 03 Oct 2016 10:43:12 +0200
From:   Sander Eikelenboom <linux@...elenboom.it>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     david.vrabel@...rix.com, jgross@...e.com, xen-devel@...ts.xen.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen/x86: Initialize per_cpu(xen_vcpu, 0) a little earlier

On 2016-10-03 00:45, Boris Ostrovsky wrote:
> xen_cpuhp_setup() calls mutex_lock() which, when CONFIG_DEBUG_MUTEXES
> is defined, ends up calling xen_save_fl(). That routine expects
> per_cpu(xen_vcpu, 0) to be already initialized.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Reported-by: Sander Eikelenboom <linux@...elenboom.it>
> ---
> Sander, please see if this fixes the problem. Thanks.

Hi Boris,

I have tested it and it fixes the dom0 crash in early boot for me.
Thanks again for investigating and the swift fix !

--
Sander


>  arch/x86/xen/enlighten.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 366b6ae..96c2dea 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1644,7 +1644,6 @@ asmlinkage __visible void __init 
> xen_start_kernel(void)
>  	xen_initial_gdt = &per_cpu(gdt_page, 0);
> 
>  	xen_smp_init();
> -	WARN_ON(xen_cpuhp_setup());
> 
>  #ifdef CONFIG_ACPI_NUMA
>  	/*
> @@ -1658,6 +1657,8 @@ asmlinkage __visible void __init 
> xen_start_kernel(void)
>  	   possible map and a non-dummy shared_info. */
>  	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
> 
> +	WARN_ON(xen_cpuhp_setup());
> +
>  	local_irq_disable();
>  	early_boot_irqs_disabled = true;