Re: [PATCH V3 04/13] HV: Mark vmbus ring buffer visible to host in Isolation VM

[Tianyu Lan]

On 8/13/2021 6:20 AM, Michael Kelley wrote:
> > @@ -474,6 +482,13 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> >   	if (ret)
> >   		return ret;
> >
> > +	ret = set_memory_decrypted((unsigned long)kbuffer,
> > +				   HVPFN_UP(size));
> > +	if (ret) {
> > +		pr_warn("Failed to set host visibility.\n");
> Enhance this message a bit.  "Failed to set host visibility for new GPADL\n"
> and also output the value of ret.

OK. This looks better. Thanks.

> > @@ -539,6 +554,10 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> >   	/* At this point, we received the gpadl created msg */
> >   	*gpadl_handle = gpadlmsg->gpadl;
> >
> > +	channel->gpadl_array[index].size = size;
> > +	channel->gpadl_array[index].buffer = kbuffer;
> > +	channel->gpadl_array[index].gpadlhandle = *gpadl_handle;
> > +
> I can see the merits of transparently stashing the memory address and size
> that will be needed by vmbus_teardown_gpadl(), so that the callers of
> __vmbus_establish_gpadl() don't have to worry about it.  But doing the
> stashing transparently is somewhat messy.
>
> Given that the callers are already have memory allocated to save the
> GPADL handle, a little refactoring would make for a much cleaner solution.
> Instead of having memory allocated for the 32-bit GPADL handle, callers
> should allocate the slightly larger struct vmbus_gpadl that you've
> defined below.  The calling interfaces can be updated to take a pointer
> to this structure instead of a pointer to the 32-bit GPADL handle, and
> you can save the memory address and size right along with the GPADL
> handle.  This approach touches a few more files, but I think there are
> only two callers outside of the channel management code -- netvsc
> and hv_uio -- so it's not a big change.

Yes, this is a good suggestion and Will update in the next version.

> > @@ -859,6 +886,19 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle)
> >   	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
> >
> >   	kfree(info);
> > +
> > +	/* Find gpadl buffer virtual address and size. */
> > +	for (i = 0; i < VMBUS_GPADL_RANGE_COUNT; i++)
> > +		if (channel->gpadl_array[i].gpadlhandle == gpadl_handle)
> > +			break;
> > +
> > +	if (set_memory_encrypted((unsigned long)channel->gpadl_array[i].buffer,
> > +			HVPFN_UP(channel->gpadl_array[i].size)))
> > +		pr_warn("Fail to set mem host visibility.\n");
> Enhance this message a bit: "Failed to set host visibility in GPADL teardown\n".
> Also output the returned error code to help in debugging any occurrences of
> a failure
Yes, agree. Will update.

Thanks.