Re: [PATCH] Remove a set operation for VCPU_KICK_SOFTIRQ when post interrupt to vm.

["Liuqiming (John)" <john.liuqiming@huawei.com>]

I believe this also has something to do with a windows guest boot hang 
issue.

It randomly occured, when boot a guest has windows 2008 os and pv-driver 
installed.
The boot process hangs when wait xenstored replay event signal.

It can be reproduced after hundreds reboot using the xen staging branch.
But after I changed this code the hang issue can not reproduce.

Any Ideas?

On 2015/9/7 22:46, - wrote:
> From: liuqiming 00178499 <john.liuqiming@huawei.com>
>
> This set operation doesn't make any sense, and it will block later
> interrupt injected into vm (by vcpu_kick or deliver_posted_intr),
> which will cause a performance issue on CPU supporting posted-interrupt.
>
> Signed-off-by: Qiming Liu <john.liuqiming@huawei.com>
> Cc: Yang Zhang <yang.z.zhang@Intel.com>
> ---
>   xen/arch/x86/hvm/vmx/vmx.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 2582cdd..9480b44 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1681,7 +1681,7 @@ static void __vmx_deliver_posted_interrupt(struct vcpu *v)
>       {
>           unsigned int cpu = v->processor;
>   
> -        if ( !test_and_set_bit(VCPU_KICK_SOFTIRQ, &softirq_pending(cpu))
> +        if ( !test_bit(VCPU_KICK_SOFTIRQ, &softirq_pending(cpu))
>                && (cpu != smp_processor_id()) )
>               send_IPI_mask(cpumask_of(cpu), posted_intr_vector);
>       }