linux-kernel - Re: [PATCH] xen: disable PV spinlocks on HVM

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Date:	Wed, 07 Sep 2011 14:24:26 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	stefano.stabellini@...citrix.com
CC:	konrad.wilk@...cle.com, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com
Subject: Re: [PATCH] xen: disable PV spinlocks on HVM

On 09/06/2011 09:41 AM, stefano.stabellini@...citrix.com wrote:
> From: Stefano Stabellini <stefano.stabellini@...citrix.com>
>
> PV spinlocks cannot possibly work with the current code because they are
> enabled after pvops patching has already been done, and because PV
> spinlocks use a different data structure than native spinlocks so we
> cannot switch between them dynamically. A spinlock that has been taken
> once by the native code (__ticket_spin_lock) cannot be taken by
> __xen_spin_lock even after it has been released.
>
> Reported-by: Stefan Bader <stefan.bader@...onical.com>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> ---
>  arch/x86/xen/smp.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index e79dbb9..51339b4 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -522,7 +522,6 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
>  	WARN_ON(xen_smp_intr_init(0));
>  
>  	xen_init_lock_cpu(0);
> -	xen_init_spinlocks();
>  }

Should I add this back here on the pv ticketlock branch?

    J

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