[Xen-devel] Re: [PATCH 02/17] x86: add io_apic_ops to allow interception

[Ingo Molnar <mingo@xxxxxxx>]

* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> ---
>  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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