Re: [Qemu-devel] [PATCH v4 5/5] i8259: fix dynamically masking slave IRQs with IMR register

[Jan Kiszka]

On 2012-09-03 18:33, Paolo Bonzini wrote:
> Il 03/09/2012 18:30, Avi Kivity ha scritto:
>>>>>> The values above are what every user of the PIC cascaded on our targets
>>>>>>>>>> must program to use them. So We will find them in the state once any
>>>>>>>>>> relevant guest code was able to run (e.g. the BIOS).
>>>>>>>>>>
>>>>>> Suppose the bios has not run yet?
>>>>
>>>> Then you transmit the subsection.
>> And the migration fails.  Needlessly, since icw3 == 0 doesn't affect
>> guest operation.
> 
> But the point of subsections is to succeed migration in the common case,
> assuming there is more than one case that doesn't affect guest operation.

The point is that the common case is icw3 = 4 (for the master), not 0.
And if we don't save that case, we must save the rest. If we don't save
this as well, we lose state information. This can't work.

Jan

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