RE: [PATCH V6 7/8] Drivers: hv: vmbus: Add SNP support for VMbus channel initiate message

[Michael Kelley]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Saturday, October 2, 2021 7:40 AM
> 
> 
> On 10/2/2021 9:26 PM, Michael Kelley wrote:
> >> @@ -303,10 +365,26 @@ void vmbus_disconnect(void)
> >>   		vmbus_connection.int_page = NULL;
> >>   	}
> >>
> >> -	hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[0]);
> >> -	hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[1]);
> >> -	vmbus_connection.monitor_pages[0] = NULL;
> >> -	vmbus_connection.monitor_pages[1] = NULL;
> >> +	if (hv_is_isolation_supported()) {
> >> +		memunmap(vmbus_connection.monitor_pages[0]);
> >> +		memunmap(vmbus_connection.monitor_pages[1]);
> > The matching memremap() calls are made in vmbus_connect() only in the
> > SNP case.  In the non-SNP case, monitor_pages and monitor_pages_original
> > are the same, so you would be doing an unmap, and then doing the
> > set_memory_encrypted() and hv_free_hyperv_page() using an address
> > that is no longer mapped, which seems wrong.   Looking at memunmap(),
> > it might be a no-op in this case, but even if it is, making them conditional
> > on the SNP case might be a safer thing to do, and it would make the code
> > more symmetrical.
> >
> 
> Yes, memumap() does nothing is the non-SNP CVM and so I didn't check CVM
> type here. I will add the check in the next version.
> 
> Thanks.
> 

I would also be OK with just adding a comment to that effect, just so someone
looking at the code in the future understands that there's not a problem.
Your call.

Michael