Re: [PATCH RFC] pass write value to in_range pointers

From: Avi Kivity
Date: Tue Jun 23 2009 - 05:51:40 EST

On 06/22/2009 07:08 PM, Michael S. Tsirkin wrote:
On Mon, Jun 22, 2009 at 11:45:00AM -0400, Gregory Haskins wrote:
Michael S. Tsirkin wrote:
It seems that a lot of complexity and trickiness with iosignalfd is
handling the group/item relationship, which comes about because kvm does
not currently let a device on the bus claim a write transaction based on the
value written. This could be greatly simplified if the value written
was passed to the in_range check for write operation. We could then
simply make each kvm_iosignalfd a device on the bus.

What does everyone think of the following lightly tested patch?

Hi Michael,
Its interesting, but I am not convinced its necessary. We created the
group/item layout because iosignalfds are unique in that they are
probably the only IO device that wants to do some kind of address

We actually already have aliasing: is_write flag is used for this
purpose. Actually, it's possible to remove is_write by passing
a null pointer in write_val for reads. I like this a bit less as
the code generated is less compact ... Avi, what do you think?

Greg, won't Michael's patch eliminate a big chunk from your iosignalfd patches? Seems like a win to me.

One is enough :)
Seriously, do you see that this saves you all of RCU, linked lists and
counters? You don't need to keep track of iofds, you don't need to
implement your own lookup logic - you just use the kvm device
and that's it.


error compiling committee.c: too many arguments to function

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