Re: [Qemu-devel] [RFC v1] Add declarations for hierarchical memory region API

[Avi Kivity <avi@redhat.com>]

On 05/19/2011 10:07 PM, Alex Williamson wrote:
> On Thu, 2011-05-19 at 10:12 -0400, Avi Kivity wrote:
> >  The memory API separates the attributes of a memory region (its size, how
> >  reads or writes are handled, dirty logging, and coalescing) from where it
> >  is mapped and whether it is enabled.  This allows a device to configure
> >  a memory region once, then hand it off to its parent bus to map it according
> >  to the bus configuration.
> >
> >  Hierarchical registration also allows a device to compose a region out of
> >  a number of sub-regions with different properties; for example some may be
> >  RAM while others may be MMIO.
>
> >  +    /* Guest-visible constraints: */
> >  +    struct {
> >  +        /* If nonzero, specify bounds on access sizes beyond which a machine
> >  +         * check is thrown.
> >  +         */
> >  +        unsigned min_access_size;
> >  +        unsigned max_access_size;
>
> Do we always support all access sizes between min and max?

As far as I can tell, yes.

> This might
> be easier to describe as a bitmap of supported power of 2 access sizes.

This is uglier to initialize.  However we can provide #defines for 
common use (MEM_ACCESS_BYTE_TO_LONG, MEM_ACCESS_LONG).

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.