linux-kernel - Re: [PATCH 02/17] x86: add io_apic

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Date:	Mon, 25 May 2009 05:54:46 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH 02/17] x86: add io_apic_ops to allow interception


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> 
> Xen dom0 needs to paravirtualize IO operations to the IO APIC, so add
> a io_apic_ops for it to intercept.  Do this as ops structure because
> there's at least some chance that another paravirtualized environment
> may want to intercept these.
> 
> [Impact: indirect IO APIC access via io_apic_ops]
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> ---
>  arch/x86/include/asm/io_apic.h |    9 +++++++
>  arch/x86/kernel/apic/io_apic.c |   50 +++++++++++++++++++++++++++++++++++++--
>  2 files changed, 56 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
> index 9d826e4..8cbfe73 100644
> --- a/arch/x86/include/asm/io_apic.h
> +++ b/arch/x86/include/asm/io_apic.h
> @@ -21,6 +21,15 @@
>  #define IO_APIC_REDIR_LEVEL_TRIGGER	(1 << 15)
>  #define IO_APIC_REDIR_MASKED		(1 << 16)
>  
> +struct io_apic_ops {
> +	void (*init)(void);
> +	unsigned int (*read)(unsigned int apic, unsigned int reg);
> +	void (*write)(unsigned int apic, unsigned int reg, unsigned int value);
> +	void (*modify)(unsigned int apic, unsigned int reg, unsigned int value);
> +};
> +
> +void __init set_io_apic_ops(const struct io_apic_ops *);

ok, could you please turn the whole IO-APIC code into a driver 
framework? I.e. all IO-APIC calls outside of 
arch/x86/kernel/apic/io_apic.c should be to some io_apic-> method.

The advantage will be a proper abstraction for all IO-APIC details - 
not just a minimalistic one for Xen's need.

Also, please name it 'struct io_apic' - similar to the 'struct apic' 
naming we have for the local APIC driver structure.

Thanks,

	Ingo
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