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Re: [EXTERNAL] [PATCH 2/2] target/ppc: Fix ISA v3.0 (POWER9) slbia imple

From: David Gibson
Subject: Re: [EXTERNAL] [PATCH 2/2] target/ppc: Fix ISA v3.0 (POWER9) slbia implementation
Date: Thu, 19 Mar 2020 16:22:06 +1100

On Thu, Mar 19, 2020 at 07:46:54AM +1100, Benjamin Herrenschmidt wrote:
> On Wed, 2020-03-18 at 18:08 +0100, Cédric Le Goater wrote:
> > On 3/18/20 5:41 AM, Nicholas Piggin wrote:
> > > Linux using the hash MMU ("disable_radix" command line) on a POWER9
> > > machine quickly hits translation bugs due to using v3.0 slbia
> > > features that are not implemented in TCG. Add them.
> > 
> > I checked the ISA books and this looks OK but you are also modifying
> > slbie.
> For the same reason, I believe slbie needs to invalidate caches even if
> the entry isn't present.
> The kernel will under some circumstances overwrite SLB entries without
> invalidating (because the translation itself isn't invalid, it's just
> that the SLB is full, so anything cached in the ERAT is still
> technically ok).
> However, when those things get really invalidated, they need to be
> taken out, even if they no longer have a corresponding SLB entry.

Right, the slbie change is certainly correct, but it doesn't match
what the commit message says this is doing.  Nick, can you split that
out please.

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_!

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