Re: [Qemu-devel] [RFC PATCH RDMA support v4: 03/10] more verbose documentation of the RDMA transport

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

Very nice catch. Yes, I didn't think about that.

Thanks.

On 03/21/2013 02:11 AM, Michael S. Tsirkin wrote:
>
> I really shouldn't break COW if you don't request LOCAL_WRITE.
> I think it's a kernel bug, and apparently has been there in the code since the
> first version: get_user_pages parameters swapped.
>
> I'll send a patch. If it's applied, you should also
> change your code from
>
> +                                IBV_ACCESS_LOCAL_WRITE |
> +                                IBV_ACCESS_REMOTE_WRITE |
> +                                IBV_ACCESS_REMOTE_READ);
>
> to
>
> +                                IBV_ACCESS_REMOTE_READ);
>
> on send side.
> Then, each time we detect a page has changed we must make sure to
> unregister and re-register it. Or if you want to be very
> smart, check that the PFN didn't change and reregister
> if it did.
>
> This will make overcommit work.
>