Re: [Qemu-devel] [RFC PATCH 09/10] spapr_iommu: Provide a function to switch a TCE table to allowing VFIO

[Thomas Huth <thuth@redhat.com>]

On 17/09/15 18:54, Alex Williamson wrote:
> On Thu, 2015-09-17 at 23:09 +1000, David Gibson wrote:
>> Because of the way non-VFIO guest IOMMU operations are KVM accelerated, not
>> all TCE tables (guest IOMMU contexts) can support VFIO devices.  Currently,
>> this is decided at creation time.
>>
>> To support hotplug of VFIO devices, we need to allow a TCE table which
>> previously didn't allow VFIO devices to be switched so that it can.  This
>> patch adds an spapr_tce_need_vfio() function to do this, by reallocating
>> the table in userspace if necessary.
>>
>> Currently this doesn't allow the KVM acceleration to be re-enabled if all
>> the VFIO devices are removed.  That's an optimization for another time.
> 
> 
> Same comment as previous patch, spapr_tce_need_userspace_table() (or
> something) makes the code much more self documenting.

May I also add the using the word "need" in a function name is could be
a little bit confusing here? It's maybe just me, but if I read
..._need_...() I first think of a function that just checks something
and returns a boolean for yes or no, not of a function that changes
something.
Could you maybe use something like "..._change_to_..." instead?

 Thomas