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Date: Fri, 25 Apr 2008 23:44:43 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Jens Axboe <jens.axboe@oracle.com>
CC: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, npiggin@suse.de,
       torvalds@linux-foundation.org, peterz@infradead.org, sam@ravnborg.org
Subject: Re: [PATCH 2/11] x86: convert to generic helpers for IPI function
 calls
References: <1208890227-24808-1-git-send-email-jens.axboe@oracle.com> <1208890227-24808-3-git-send-email-jens.axboe@oracle.com>
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Jens Axboe wrote:
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
>   
[...]
> +void arch_send_call_function_single_ipi(int cpu)
>  {
>   
[...]
> +void arch_send_call_function_ipi(cpumask_t mask)
>  {
>   
[...]
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> +void arch_send_call_function_ipi(cpumask_t mask)
> +{
>   
[...]
> +void arch_send_call_function_single_ipi(int cpu)
> +{
> +	xen_send_IPI_mask(cpumask_of_cpu(cpu), XEN_CALL_FUNCTION_SINGLE_VECTOR);
>  

Xen vs native is a runtime choice, so you can't just statically define 
arch_send_call_function(_single)_ipi for each.  You need to define the 
arch_* functions once, make them call via smp_ops, and call into the 
respective native and Xen versions of the ipi functions.

Aside from that it looks good, with a very appealing code size reduction.

    J