Re: [PATCH 04/13] KVM: PPC: Ultravisor: Use UV_WRITE_PATE ucall to register a PATE

[Ram Pai <linuxram@us.ibm.com>]

On Wed, Jan 23, 2019 at 10:48:20AM +1100, Paul Mackerras wrote:
> On Tue, Jan 22, 2019 at 07:59:35AM -0800, Ram Pai wrote:
> > From: Michael Anderson <andmike@linux.ibm.com>
> > 
> > The Nest_MMU needs to know the address of the Partition table (PT).
> > However the PT is in secure memory, and nestMMU cannot access secure
> > memory.  Hence hypevisor will continue to use a Partition table of
> > its own. It will have PATE entries for HV and for Normal virtual
> > machines. The same entries are also in the UV's PT.  The HV's PT
> > is programmed with the nest MMU.
> 
> This isn't a good patch description.  It's confusing because it
> doesn't start with the primary motivation of the patch - which is that
> when running under an ultravisor, the ultravisor controls the real
> partition table and has it in secure memory where the hypervisor can't
> access it, and therefore we (the HV) have to do a ucall whenever we
> want to update an entry.  Once you have explained that, then you can
> explain the secondary aspect of the patch, which is that the HV still
> keeps a copy of its view of the partition table in normal memory so
> that the nest MMU can access it.
> 
> > Suggested-by: Ryan Grimm <grimm@linux.vnet.ibm.com>
> > Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
> > [device node name to ibm,ultravisor]
> > Signed-off-by: Michael Anderson <andmike@linux.ibm.com>
> > Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> 
> If Michael Anderson wrote the patch and sent it to you, and you sent
> it to the list, why is Maddy's signoff relevant?  Was the original
> version of the patch actually written by Maddy?

Yes. this patch description needs a good amount work.  A couple of
related patches; some by Michael and some by me and some bug fixes by Maddy,
were merged  leading to this signoff cocktail and incoherent
description.

This was my first attempt to bring a logical order to
our internal set of patches, which I agree has some more way to go. :(

Thanks,
RP