Re: [kvm-ppc-devel] [PATCH 1 of 3] Move x86 kvmcallback structure to kvmctl-x86.h header

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Hollis Blanchard wrote:
> On Sun, 2007-10-28 at 21:11 -0500, Anthony Liguori wrote:
>   
>> int (*io_write)(void *opaque, int as, uint64_t addr, uint64_t data,
>> int size);
>>
>> Where as is a #define representing the address space (on x86, there is
>> the PIO and MMIO address spaces, on PPC, there is just MMIO).
>>     
>
> So the implementation would look something like this:
>
> int io_write(void *opaque, int as, uint64_t addr, uint64_t data, int
> size) {
>         io_handler_t cb;
>         
>         switch (as) {
>         case MMIO:
>                 cb = io_table_lookup(&mmio_table, ...)
>                 break;
> #ifdef HAS_PIO
>         case PIO:
>                 cb = io_table_lookup(&pio_table, ...)
>                 break;
> #endif
> #ifdef HAS_DCR
>         case DCR:
>                 cb = io_table_lookup(&dcr_table, ...)
>                 break;
> #endif
>         default:
>                 cb = NULL;
>         }
>         
>         if (cb)
>                 return cb(...);
>         
>         printk("error");
>         return -EINVAL;
> }
>
> Sounds fine to me.
>   

You could certainly get even more clever and have the arch backend 
register the appropriate tables based on the as type but that's merely 
an implementation detail.  The key observation, that I believe is 
correct, is that all architectures have one or more IO "address spaces" 
that have at max a 64-bit address space and support at max 64-bit 
input/output operations.  Once that assumption is made, almost all IO 
code becomes common.

Regards,

Anthony Liguori



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