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

    * 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


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