Re: [PATCH 5/5] ioeventfd: Introduce KVM_IOEVENTFD_FLAG_SOCKET

Pekka Enberg
2011-07-13T10:56:19Z

On Wed, Jul 13, 2011 at 1:26 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
> The problem is that if we received a signal during the read notification
> the write and before receiving the read, we have to go back to
> userspace.
>
> This means that userspace will see same read request twice (once in the
> socket and once in the MMIO exit).

So the problem is only in ioeventfd_read() if socket_write() succeeds
but socket_read() fails? If so, can we do the socket_read() somewhere
else in the code which is able to restart it?

AFAICT, both ioeventfd_read() and ioeventfd_write() should -ENOSUPP if
socket_write() fails. If socket_write() succeeds, we should return
-EINTR and teach vcpu_mmio_read() and kernel_pio() to KVM_EXIT_INTR in
those cases. We'll can just restart the read, no? The only
complication I can see is that ioeventfd_read() needs to keep track if
it did the socket_write() already or not.

Pekka