Re: [Qemu-devel] [PATCH] spapr: Remove support for explicitly allocated RMAs

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, May 03, 2018 at 09:19:34AM +0200, Thomas Huth wrote:
> On 03.05.2018 09:10, David Gibson wrote:
> > Current POWER cpus allow for a VRMA, a special mapping which describes a
> > guest's view of memory when in real mode (MMU off, from the guest's point
> > of view).  Older cpus didn't have that which meant that to support a guest
> > a special host-contiguous region of memory was needed to give the guest its
> > Real Mode Area (RMA).
> > 
> > KVM used to provide special calls to allocate a contiguous RMA for those
> > cases.  This was useful in the early days of KVM on Power to allow it to be
> > tested on PowerPC 970 chips as used in Macintosh G5 machines.  Now, those
> > machines are so old as to be almost irrelevant.
> 
> I still got my YDL PowerStation somewhere in a corner ... but well,
> true, I haven't turned on its power since a year or two... or three...
> 
> > The normal qemu deprecation process would require this to be marked
> > deprecated then removed in 2 releases.  However, this can only be used
> > with corresponding support in the host kernel - which was dropped
> > years ago (in c17b98cf "KVM: PPC: Book3S HV: Remove code for PPC970
> > processors" of 2014-12-03 to be precise).  Therefore it should be ok
> > to drop this immediately.
> 
> OK, fair.
> 
> > Just to be clear this only affects *KVM* guests with PowerPC 970, and those
> > already require an ancient host kernel.  TCG guests with PowerPC 970 should
> > still work.
> 
> Just to be sure: kvm-pr will continue to work on a 970 host, right? In
> that case:

Yes, KVM PR should be fine.  Not that I've tested, but I see no reason
it would break.  I'll clarify that in the message.

> Acked-by: Thomas Huth <thuth@redhat.com>
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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