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Date: Fri, 09 Aug 2013 09:41:15 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] memory: Provide separate handling of
 unassigned io ports accesses
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-devel <qemu-devel@nongnu.org>

Il 08/08/2013 17:43, Jan Kiszka ha scritto:
> On 2013-08-08 17:33, Peter Maydell wrote:
>> On 3 August 2013 09:31, Jan Kiszka <jan.kiszka@web.de> wrote:
>>> --- a/ioport.c
>>> +++ b/ioport.c
>>> @@ -44,6 +44,22 @@ typedef struct MemoryRegionPortioList {
>>>      MemoryRegionPortio ports[];
>>>  } MemoryRegionPortioList;
>>>
>>> +static uint64_t unassigned_io_read(void *opaque, hwaddr addr, unsigned size)
>>> +{
>>> +    return -1UL;
>>
>> This should probably be "-1ULL", otherwise we'll return
>> different values on 32 bit and 64 bit hosts. (Actually
>> managing a 64 bit read of the i/o space is pretty
>> unlikely, though possibly alpha memory-mapped via the
>> PCI space might let you do it.)
> 
> No problem with changing this - but wouldn't 64-bit i/o accesses be a
> bug? It's not allowed according to PCI, no device can handle it
> (officially), so no arch should forward such requests from mmio, rather
> break them up first.

Yes, the impl.max_access_size should never be 8.  Though 1ULL would be
clearer perhaps.

Paolo