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Re: [Qemu-ppc] [PATCH 23/25] PPC: e500: dt: use target_phys_addr_t for r


From: Scott Wood
Subject: Re: [Qemu-ppc] [PATCH 23/25] PPC: e500: dt: use target_phys_addr_t for ramsize
Date: Thu, 31 May 2012 17:24:17 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1

On 05/31/2012 05:18 PM, Alexander Graf wrote:
> 
> On 01.06.2012, at 00:07, Scott Wood wrote:
> 
>> On 05/30/2012 06:00 AM, Alexander Graf wrote:
>>> We're passing the ram size as uint32_t, capping it to 32 bits atm.
>>> Change to target_phys_addr_t (uint64_t) to make sure we have all
>>> the bits.
>>
>> Wouldn't ram_addr_t be more appropriate?
> 
> I never quite grasped the difference, but wasn't ram_addr_t something for the 
> host?

I don't fully understand QEMU's RAM handling, but from what I recall RAM
is treated differently from arbitrary guest physical addresses, with a
QEMU-internal contiguous address space.  Guest RAM needs to be mappable
by QEMU as well as the target, so ram_addr_t is 32-bit on a 32-bit host,
even if target_phys_addr_t is different.

But again, it was a while ago that I looked at this, and I didn't fully
understand it then, so I may be missing or misremembering something.

-Scott




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