On 07/04/2011 01:49 PM, Michael S. Tsirkin wrote:
On Mon, Jul 04, 2011 at 01:27:45PM +0300, Avi Kivity wrote:
> I'd like to be able to forward an entire PCI BAR
> over a pipe. That means sending the address/data/length tuple, and
> both read and write support.
>
> >> Is the write guaranteed atomic? We probably need serialization here.
> >
> >afaik vfs_write is just a wrapper to the write() function of the
> >underlying fs so it should be atomic, no?
>
> write() isn't atomic in general. It is for pipes under certain
> circumstances, but there is no guarantee that the circumstances
> apply, or that the fd is in fact a pipe.
So the above makes it tricky to pass structured data
which is> 1 byte in size over a pipe. We could build an in-kernel API
(not sure how useful it would be for userspace) to do
an atomic write or fail (instead of a partial write),
but we'll still need to handle failures.
We don't need atomicity after a failure, just under normal operation,
and that can be provided by a mutex.
It's not trivial since a single fd might be associated with several region.
--
error compiling committee.c: too many arguments to function
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