KVM: PPC: Book3S PR: Rework SLB switching code

On LPAR guest systems Linux enables the shadow SLB to indicate to the
hypervisor a number of SLB entries that always have to be available.

Today we go through this shadow SLB and disable all ESID's valid bits.
However, pHyp doesn't like this approach very much and honors us with
fancy machine checks.

Fortunately the shadow SLB descriptor also has an entry that indicates
the number of valid entries following. During the lifetime of a guest
we can just swap that value to 0 and don't have to worry about the
SLB restoration magic.

While we're touching the code, let's also make it more readable (get
rid of rldicl), allow it to deal with a dynamic number of bolted
SLB entries and only do shadow SLB swizzling on LPAR systems.

Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index ad302f845e5d..d6e195e8cd4c 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -98,6 +98,9 @@ static inline void free_lppacas(void) { }
 /*
  * 3 persistent SLBs are registered here.  The buffer will be zero
  * initially, hence will all be invaild until we actually write them.
+ *
+ * If you make the number of persistent SLB entries dynamic, please also
+ * update PR KVM to flush and restore them accordingly.
  */
 static struct slb_shadow *slb_shadow;