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SubjectRe: [PATCH v7 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening
On Mon, Sep 14, 2020 at 05:29:11PM +0000, Michael Kelley wrote:
> From: Andrea Parri <parri.andrea@gmail.com> Sent: Tuesday, September 8, 2020 12:54 AM
> >
> > > > @@ -300,6 +303,22 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
> > > > kv_list[i].iov_len);
> > > > }
> > > >
> > > > + /*
> > > > + * Allocate the request ID after the data has been copied into the
> > > > + * ring buffer. Once this request ID is allocated, the completion
> > > > + * path could find the data and free it.
> > > > + */
> > > > +
> > > > + if (desc->flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {
> > > > + rqst_id = vmbus_next_request_id(&channel->requestor, requestid);
> > > > + if (rqst_id == VMBUS_RQST_ERROR) {
> > > > + pr_err("No request id available\n");
> > > > + return -EAGAIN;
> > > > + }
> > > > + }
> > > > + desc = hv_get_ring_buffer(outring_info) + old_write;
> > > > + desc->trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;
> > > > +
> > >
> > > This is a nit, but the above would be clearer to me if written like this:
> > >
> > > flags = desc->flags;
> > > if (flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {
> > > rqst_id = vmbus_next_request_id(&channel->requestor, requestid);
> > > if (rqst_id == VMBUS_RQST_ERROR) {
> > > pr_err("No request id available\n");
> > > return -EAGAIN;
> > > }
> > > } else {
> > > rqst_id = requestid;
> > > }
> > > desc = hv_get_ring_buffer(outring_info) + old_write;
> > > desc->trans_id = rqst_id;
> > >
> > > The value of the flags field controls what will be used as the value for the
> > > rqst_id. Having another test to see which value will be used as the trans_id
> > > somehow feels a bit redundant. And then rqst_id doesn't have to be initialized.
> >
> > Agreed, will apply in the next version.
> >
>
> In an offline conversation, Andrea has pointed out that my proposed changes
> don't work. After a second look, I'll agreed that Andrea's code is the best that
> can be done, so my comments can be ignored.

Thanks for the confirmation, Michael. So, I plan to keep this patch as
is for the next submission of the series (to be submitted shortly...).

Thanks,
Andrea

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