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Re: [Qemu-devel] [PATCH 08/20] memory: store MemoryRegionSection pointer


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH 08/20] memory: store MemoryRegionSection pointers in phys_map
Date: Thu, 8 Mar 2012 10:09:07 +0000

On 8 March 2012 09:50, Avi Kivity <address@hidden> wrote:
> On 03/07/2012 09:32 PM, Peter Maydell wrote:
>> Are we running into the "mapping devices at non-page-offsets isn't
>> supported" issue here?
>
> It wasn't supported?

Well, you used to run into the issue noted in the comment above
exec.c:register_subpage():
   The address used when calling the IO function is
   the offset from the start of the region, plus region_offset.  Both
   start_addr and region_offset are rounded down to a page boundary
   before calculating this offset.  This should not be a problem unless
   the low bits of start_addr and region_offset differ.

and for non-page-aligned IO regions we were getting bitten by
this rounding, which is why the offset passed into the read/write
function was strange.

Is that exec.c comment now out of date?

(You might recall we had a conversation about this a little while
back: http://patchwork.ozlabs.org/patch/129267/ )

-- PMM



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