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Re: [Xen-devel] qemu(-dm): aborting on wrong mmio size?

On 01/31/12 11:36, Jan Beulich wrote:
On 31.01.12 at 10:34, Laszlo Ersek<lersek@xxxxxxxxxx>  wrote:

Is it justified to kill the emulator when this happens (eg. memory
mapped IO with 64-bit operand)?

The AMD manual specifies that REX.W is ignored; the Intel manual
doesn't mention REX at all here. However, if a decoder incorrectly
decodes the guest instruction, that's a bug there. So imo qemu
validly treats this condition as fatal.

From the Itanium(R) SDM rev 2.3, I/O Port Addressing Restrictions

    For the 64MB physical I/O port block the following operations are
    undefined and may result in unpredictable processor operation;
    references larger than 4-bytes, [...]

It seems that not only a decoding failure can trigger this.


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