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

Ingo Molnar
2009-05-25T03:55:27Z

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

> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.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@citrix.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