Re: [PATCH v4 08/17] iommufd: Always setup MSI and anforce cc on kernel-managed domains

[Nicolin Chen]

On Mon, Oct 23, 2023 at 10:59:35AM -0300, Jason Gunthorpe wrote:
> On Sun, Oct 22, 2023 at 05:18:03PM -0700, Nicolin Chen wrote:
> 
> > > > And where should we add this comment? Kdoc of
> > > > the alloc uAPI?
> > > 
> > > Maybe right in front of the only enforce_cc op callback?
> > 
> > OK. How about this? Might be a bit verbose though:
> > 	/*
> > 	 * enforce_cache_coherenc must be determined during the HWPT allocation.
> > 	 * Note that a HWPT (non-CC) created for a device (non-CC) can be later
> > 	 * reused by another device (either non-CC or CC). However, A HWPT (CC)
> > 	 * created for a device (CC) cannot be reused by another device (non-CC)
> > 	 * but only devices (CC). Instead user space in this case would need to
> > 	 * allocate a separate HWPT (non-CC).
> > 	 */
> 
> Ok, fix the spello in enforce_cache_coherenc

Oops.

I also found the existing piece sorta says a similar thing:
         * Set the coherency mode before we do iopt_table_add_domain() as some
         * iommus have a per-PTE bit that controls it and need to decide before
         * doing any maps. 

So, did this and sending v3:
-        * enforce_cache_coherenc must be determined during the HWPT allocation.
+        * The cache coherency mode must be configured here and unchanged later.