Re: [Xen-devel] trap bounce flags

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 25/4/07 11:10, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:

>> - from the above, why is it that only the lower byte (if anything) needs
>> clearing?
> 
> Really it's a one-byte field: it's consistently treated that way in asm
> code. The upper byte is always zero. We should probably make the field
> explicitly uint8_t. Agree?

FYI, we need to clear that field usually because the contents are one-shot
but the structure itself is permanent and checked on every return to guest.
A non-zero flags field is what we use to indicate whether the structure is
'primed' or not. So the passing in of a different, non-one-shot, structure
on the direct-int80 path is a bit abusive of the interface. But I think we
can live with it if we reset the flags field manually and include a comment.
:-)

 -- Keir


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