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

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Date:	Tue, 06 Sep 2011 10:18:08 -0700
From:	Stefan Bader <stefan.bader@...onical.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	stefano.stabellini@...citrix.com, xen-devel@...ts.xensource.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen: disable PV spinlocks on HVM

On 06.09.2011 10:02, Konrad Rzeszutek Wilk wrote:
> On Tue, Sep 06, 2011 at 05:41:47PM +0100, 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.
> 
> Let me stick it on my 3.1-rc5 bug-fix list and add stable@...nel.org to it.
> 
> Stefan, if you have some time this week, and can test it - I can also
> stick 'Tested-by' if you would like.
> 
> Thinking to send the patches on Friday.
> 
>>
>> 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();
>>  }
>>  
>>  static int __cpuinit xen_hvm_cpu_up(unsigned int cpu)
>> -- 
>> 1.7.2.3
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@...ts.xensource.com
>> http://lists.xensource.com/xen-devel

I'll try. Currently I only got a version tested that takes out the
xen_init_lock_cpu calls as well.

-Stefan
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